Avian Flu Diary

Preprint: The canine respiratory epithelium is a permissive ecosystem for influenza interspecies transmission and emergence

2026-06-09T06:50:58.304-04:00

#19,196

Until 2004, dogs were considered relatively immune to influenza, but that changed abruptly when an equine H3N8 virus spilled over to dogs at a Florida racetrack, and began its world tour.

Three years later, an avian H3N2 virus spilled over to dogs in South Korea, and spread across Asia, eventually arriving in the United States in 2015.

In 2010, in Morens & Taubenberger on Influenza’s History, we looked a a fascinating 11-page historical review of Influenza outbreaks amongst a variety of hosts (human, avian, equine, porcine, canine, etc.) going back more than 3,000 years by Jeffrey K. Taubenberger and David Morens.

They cited a number of pandemics where anecdotal accounts mentioned dogs falling ill, either before - or concurrent to - when human cases emerged.

Since then we've looked at a lot of studies on dogs and flu, including:

In late 2012, in China: Avian-Origin Canine H3N2 Prevalence In Farmed Dogs, we looked at a study that found a newly emergent avian origin H3N2 virus prevalent in pet and farmed dog populations in southern China.

In 2015, in Korea Finds More Dogs With H5N8 Antibodies, we saw evidence of HPAI infection in dogs.

Also in 2014, in Study: Dogs As Potential `Mixing Vessels’ For Influenza - we looked at the ability of different influenza strains (canine, equine and human) to infect, and replicate in, canine tracheal tissues.

In 2015, researchers reported finding Influenza A(H6N1) In Dogs, Taiwan

Again in 2015, in Virology J: Human-like H3N2 Influenza Viruses In Dogs - Guangxi, China, we looked at the discovery two H3N2 CIVs possessing high homology with human/swine influenza viruses.

In 2023 we looked at a lengthy (57-page) preprint called Increased Public Health Threat of Avian-origin H3N2 Influenza Virus During Evolution in Dogs from researchers in China who warned on the continued evolution of canine H3N2, which appears to be moving towards becoming a more `humanized' virus.

More recently (2025) we looked at A Brief History of Influenza A in Canines & Canadian Report On A Recent Fatal H5N1 Dog Infection.

While dogs are more apt to have less severe flu illness than cats - making infections easier to miss - there is little doubt they are susceptible. Unknown, however, is whether they are mostly a dead-end host, or if they are capable to transmitting the virus to others.

Today we've got a preprint from researchers in the UK which attempts to better understand the risks. Using canine lung explants, they find that dogs are a plausible host for influenza reassortment, as they contain both human-type (α2,6) and avian-type (α2,3) receptor cells.

The caveats being that this is an ex vivo study, and is subject to a number of limitations (see below), and there is currently no evidence that novel influenza viruses are spreading efficiently among canines.

But the only constant with influenza viruses is that they change, making today's status tenuous at best. Due to its length, I've only posted some excerpts. Follow the link to read the report in its entirety.

The canine respiratory epithelium is a permissive ecosystem for influenza interspecies transmission and emergence
Hanting Chen, Jack Hassard, Jiayun Yang, Callum Magill, Toby Carter, Jean-Remy Sadeyen, Aimi Ito, Clio Duerr, Hannah Rose Montgomery, Savitha Raveendran, Kieran Dee, Maximillian N J Woodall, Grace B Tyson, Maria M Afonso, Verena Schultz, Claire Mary Smith, Margaret J Hosie, Stuart Haslam, Munir J Iqbal, Pablo R Murcia

doi: https://doi.org/10.64898/2026.06.04.730051
This article is a preprint and has not been certified by peer review

Preview PDF

Abstract

The outcome of virus spillover ranges from dead-end infections to pandemics and is underpinned by host-pathogen interactions as well as evolutionary and epidemiological processes. The emergence of novel influenza A viruses (IAVs) has been associated with reassortment events involving multiple species, highlighting the importance of reservoir and intermediate hosts in viral emergence.

Highly pathogenic H5N1 IAVs of the 2.3.4.4b genotype have caused a panzootic affecting a broad range of mammals. The role of dogs -arguably the most popular companion animal and a natural host of IAVs- in the ecology of IAVs under this new zooepidemiological scenario is unknown. To address this, we characterised the glycome of the dog respiratory epithelium, infected canine tracheal explants with multiple IAVs (including canine H3N2 and H3N8, equine H3N8, avian H3N8 and H5N1, swine H1N1, human H1N1 and H3N2, and bovine H5N1 viruses), and determined their cellular tropism.

We show that the respiratory tract of dogs presents abundant sialylated glycans known to act as IAV receptors. Further, most IAVs (including 2.3.4.4b viruses) infected and replicated in dog tracheas, targeting mainly ciliated cells. Serological testing showed evidence of influenza spillover infections in dogs from the UK.

Overall, our results show that the canine respiratory tract can provide a suitable environment for the generation of new IAVs. Given the multi-host contact networks of dogs in nature, they could act as recipients, bridging hosts, and/or mixing vessels for multiple IAV lineages, playing a central role in the ecology of influenza emergence.

(SNIP)
Our results suggest that dogs could act as a bridging species for the emergence of novel IAVs, including the H5N1 2.3.4.4b genotype. Serological studies in North America and Europe show that hunting dogs are routinely exposed to H5N1 IAVs 53,54.
Vaccination of high-risk dog subpopulations could reduce the risk ofinter species infections (avian-to-dog and dog-to-human) and should be considered as preventative measures.
This study has various limitations. Tracheal explants represent a significant portion of the airways, but this experimental system does not include the upper respiratory tract, the bronchial tree, nor the pulmonary parenchyma, which are likely to exhibit different virus/host interactions due to the presence of different cell types.
Further, explants lack systemic responses that are normally mounted during viral infections. Despite these limitations, our results are consistent with observations reported in field studies 59,60 and experimental in vivo infections 26,27
In sum, influenza spillover and emergence require a succession of processes that occur at different scales8. As the canine respiratory tract is a suitable ecosystem for IAV infection and reassortment and dogs routinely interact with multiple species that support endemic IAVs, dogs could facilitate the flow of virus between sympatric species. Targeted approaches to reduce the risk of IAV infections in dogs should be part of preparedness efforts to control influenza cross-species switching.

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USDA: 2 More Screwworm Detections in Texas

2026-06-08T09:48:15.669-04:00

USDA Screwworm Dashboard -Updated

Update: The USDA has clarified that the dog mentioned infected in yesterday's post was from New Mexico, not Texas.

#19,195

Although the USDA's website and Screwworm Dashboard (above) have not been updated yet, this morning the USDA emailed the following update, which adds two more cases - and importantly - from 2 new counties.

The calf in La Salle county is adjacent to Zavala County, where the first two cases were identified, but the dog in Andrews County is roughly 300 miles north and west.

There is a possibility the dog was exposed in Mexico, but the epidemiological investigation is ongoing. I'll update this post when the USDA updates their website.

(via Email)

USDA Confirms Two Additional Cases of New World Screwworm in the United States

The State of Texas continues to lead response with USDA support.

WASHINGTON, D.C., June 8, 2026 – Today, the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed two additional cases of New World screwworm (NWS) in the United States – a calf in La Salle County, Texas, and a dog in Andrews County, Texas.

Epidemiological investigations are ongoing for both cases. A veterinarian in Andrews County submitted the samples from the infested dog. Details on this case will be shared as they are available, but early reports indicate the dog was recently in Mexico.

NWS is a serious pest that threatens livestock, pets, wildlife, and, in rare cases, people. The larvae burrow into the living tissue of animals, causing severe wounds, animal suffering, and significant economic losses.

“Over the past week, USDA has identified and expeditiously confronted four confirmed detections of New World screwworm. While we address these instances that require immediate attention, and continue to sample suspected cases, we are simultaneously working to eradicate the pest entirely,” said Dudley Hoskins, Under Secretary for Marketing and Regulatory Programs. “We need the partnership of animal owners across the region – please stay vigilant, check your animals closely, and report anything that looks suspicious. Together, we can protect our livestock, our communities, and the health of animals nationwide.”

USDA and TAHC Response

USDA and the Texas Animal Health Commission (TAHC) continue to lead an aggressive unified response, with a total of 75 people actively responding on the ground and hundreds of additional people around the country providing laboratory diagnostics, logistics, treatment distribution, air operations, outreach, operational planning, and resource support for the response. APHIS and TAHC will continue to surge additional trained personnel as needed to ensure an effective response.

For each new case, USDA and TAHC implement actions outlined in the NWS Response Playbook, including:
Establishing and maintaining a 20km infested zone with quarantines, movement controls, and heightened surveillance around confirmed detections
Increasing trapping along the border and outside the dispersal zone
Conducting surveillance and management strategies in wildlife
Implementing targeted outreach to local producers, veterinarians, and communities
Intensified Sterile Fly Releases

USDA continues to release sterile flies over and just outside of the infested areas. To ensure sterile fly release operations can be deployed to affected areas in Texas and in northern Mexico near the border as quickly and efficiently as possible, USDA has activated the sterile fly dispersal facility at Moore Air Base in Edinburg, Texas. Sterile pupae arrived at the facility on Friday, and aerial dispersal flights originating from the base will begin tomorrow.

Because it is important to continue ongoing surveillance efforts while releasing sterile insects, it is possible that sterile NWS flies could be caught and/or reported. To ensure officials can tell the difference between sterile and wild NWS flies, USDA dyes the sterile pupae, and the dye transfers to the sterile flies when they hatch. The fluorescent green or orange dye glows under UV light and may also be visible to the naked eye. If a sterile fly is captured in a trap, this dye allows animal health officials to quickly rule the fly out as a threat. 

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EM&I: A new clade of H9N2 avian influenza virus circulating in Laos

2026-06-08T08:30:03.822-04:00

In terms of risk of emergence, the H9N2
Y280 lineage is ranked higher than H5N1

#19,194

While LPAI H9N2 may not be the most headline grabbing avian flu virus, it is quite likely the most versatile. It is highly promiscuous, reassorting easily with many other subtypes (including H5Nx and H7Nx), it has diverged into numerous clades, and it continues to accrue mammalian adaptations.

While testing and reporting of cases around the globe is limited, over the past 12 months more than 2 dozen human cases have been reported (see FluTrackers H9N2 case list).

As a result, H9N2 gets more than a little attention by researchers.

Last month, in Preprint: Outbreak of H9N2 Avian Influenza Viruses in Lesser Rhea in Peru, June-July 2025, we learned of a newly identified - and highly virulent - South American strain of H9N2.

Also last month, in Eurosurveillance: Cross-reactive human antibody responses to H9N2 influenza virus, New York, United States, 2025, we saw that ` pre-existing immunity to H9N2 in humans that is dominated by cross-reactive but largely non-neutralising antibodies, with a greater contribution from NA-directed responses.'

Last October, in China CDC Weekly: Epidemiological and Genetic Characterization of Three H9N2 Viruses Causing Human Infections, investigators reported a number of indicators of increased mammalian adaptation within the virus, including an enhanced ability to infect upper respiratory (α2,6-sialic acid) tract receptors, and a number of HA protein mutations, including; H191N, A198V, Q226L, and Q234L.

The Asian Y280/G57 lineages have shown increasing signs of mammalian adaptation (see EM&I: Enhanced Replication of a Contemporary Avian Influenza A H9N2 Virus in Human Respiratory Organoids)), while the African and Middle Eastern Lineages (mostly European G1-like) are older and less evolved.

All of which brings us to a new report, published last week in Emerging Microbes & Infections, which describes a new clade of LPAI H9N2 recently discovered in Laos.

A new clade of H9N2 avian influenza virus circulating in Laos
Jiaming Li ,Chunge Zhang ,Ren Li ,Yanqing Wang ,Rahat Ullah Khan ,Ruichang Quan
Article: 2678641 | Received 05 Feb 2026, Accepted 19 May 2026, Published online: 04 Jun 2026
https://doi.org/10.1080/22221751.2026.2678641
ABSTRACT
In 2024, we identified and sequenced 52 avian influenza A (H9N2) virus strains in Laos. Using the established H9N2 genomic classification system, a novel HA gene clade of the A/chicken/Beijing/1/94-like (BJ/94-like) lineage, designated Clade 4.6.20, was identified.

This new clade is phylogenetically distinct from the previously described clades, and the representative strains in this new Clade 4.6.20 presented a low cross reactivity to the antisera of other clades, suggesting antigenic drift of the viruses between the new Clade 4.6.20, and other clades in the dominant lineage of Clade 4.6.

In addition, all the newly identified viruses in Clade 4.6.20 possessed HA-L226 and NP-N52 mutations, which are associated with human-type receptor binding and human MxA-related innate immunity escape, respectively.

Our findings underscore the necessity of global surveillance network and cooperation to monitor the evolution of AIVs, update vaccine seed strains, and develop new vaccines with high effectiveness against H9N2 AIVs circulating globally, which threaten poultry and human health.

(SNIP)

In conclusion, the identification of a novel H9N2 clade (Clade 4.6.20) in Laos suggests that influenza viruses including both avian and human viruses may undergo undetected evolutionary changes in regions with inadequate surveillance, posing significant public health threats. This highlights the need to enhance international collaboration, improve surveillance systems, and develop new vaccines and NPIs to mitigate the increasing risks associated with cross-border viral spread and zoonotic transmission.

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This is the second `novel' LPAI H9N2 virus discovery reported in less than a month, and it comes just a couple of months after Europe's first imported H9N2 case (from West Africa).

While primarily an avian virus, LPAI H9N2 has a track record of also infecting humans, pigs, and even bats (see Preprint: The Bat-borne Influenza A Virus H9N2 Exhibits a Set of Unexpected Pre-pandemic Features).

China's attempts to control this rapidly evolving H9N2 virus with poultry vaccines have proved disappointing (see J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China).

And last year, in NPJ Vaccines: Impact of Inactivated Vaccine on Transmission and Evolution of H9N2 Avian Influenza Virus in Chickens, we saw evidence that not only had inactivated vaccines failed to prevent - or even reduce - H9N2 in China's poultry, they may have driven viral evolution (including mammalian adaptations).

Despite all of this - because it is not a high-risk H5 or H7 avian virus - H9N2 remains a `non-reportable' disease in poultry (see Terrestrial Animal Code Article 10.4.1.), allowing much of its spread and evolution to fly under the radar.

Hopefully these recent reports will spur additional surveillance, because - contrary to popular belief - what we don't know can hurt us.

ECDC MERS-CoV Update: 2 Cases Reported By Saudi Arabia in 2026

2026-06-08T07:02:55.464-04:00

#19,193

Although the number of MERS-CoV cases reported over the past few years has fallen dramatically, this high morbidity/mortality coronavirus continues to pose a significant public health threat ((Referral) Nature: Human MERS-CoV cases are falling but pose an ongoing pandemic threat) as it spreads and evolves in camels in the Middle East and Africa.

Admittedly, we've seen more than a little reluctance on the part of Middle Eastern nations to report cases. And it seems likely that cases are being missed in North and Central Africa as well (see EID Journal: Geographic Distribution of MERS-CoV among Dromedary Camels, Africa).

Both EID Journal: Estimation of Severe MERS Cases in the Middle East, 2012–2016 and Presence of Middle East respiratory syndrome coronavirus antibodies in Saudi Arabia: a nationwide, cross-sectional, serological study by Drosten & Memish et al., suggest that far more MERS-CoV cases have occurred than have been reported.

Last December, France reported 2 Travelers Returning From Arabian Peninsula Diagnosed with MERS-CoV, but thus far in 2026 all has been quiet. Saudi Arabia only reports every 6 months, but last Friday the ECDC carried a very brief report on two recent (March & April) cases.

Details are scant, but we know that one case was fatal, and the source of exposure for both cases are unknown. First the report, then I'll return with a bit more after the break.

Middle East respiratory Syndrome coronavirus (MERS-CoV) – Multi-country –Monthly update

Overview

Update: Since the previous update on 4 May 2026, and as of 1 June 2026, two new MERS cases, including one fatality, in Saudi Arabia have been reported by the World Health Organization (WHO) Eastern Mediterranean Regional Office (EMRO). Both cases are male adults and have unknown source of infection. One case had date of reporting in March 2026 and the fatal case had date of reporting in April 2026.

Summary: Since the beginning of 2026, and as of 1 June 2026, two MERS cases, including one fatality, have been reported in Saudi Arabia.

Since April 2012, and as of 1 June 2026, a total of 2 649 MERS cases, including 960 deaths, have been reported by health authorities worldwide.

Sources: ECDC MERS-CoV page | WHO MERS-CoV | ECDC factsheet for professionals | Qatar MoPH Case #1 |Qatar MoPH Case #2 | FAO MERS-CoV situation update | WHO DON Oman | WHO DON Saudi Arabia | WHO DON UAE | WHO DON Saudi Arabia 1 | WHO IHR | WHO EMRO MERS Situation report | WHO DON Saudi Arabia 2 |WHO DON Saudi Arabia 3 | WHO DON Saudi Arabia 4 | WHO DON Saudi Arabia 5 | MERS-CoV Dashboard | French Ministry of Health | WHO DON France & Saudi Arabia

ECDC assessment

Human MERS cases continue to be reported in the Arabian Peninsula. However, the number of new cases detected and reported through surveillance has dropped to the lowest level since 2014. The probability of sustained human to-human transmission among the general population in Europe remains very low and the impact of the disease in the general population is considered low. The current MERS-CoV situation remains unchanged and poses a low risk to the EU/EEA, as stated in the Rapid Risk Assessment published by ECDC on 29 August 2018.

ECDC published a technical report, 'Health emergency preparedness for imported cases of high-consequence infectious diseases', in October 2019 that is still useful for EU Member States wishing to assess their level of preparedness for a disease such as MERS. ECDC also published 'Risk assessment guidelines for infectious diseases transmitted on aircraft (RAGIDA) – Middle East respiratory syndrome coronavirus (MERS-CoV)' on 22 January 2020.ActionsECDC is monitoring this situation through its epidemic intelligence activities and reports on a monthly basis or when new epidemiological information is available

Prior to COVID's emergence in late 2019, MERS-CoV was the top contender for sparking a coronavirus pandemic, sporting a high mortality rate (>30%), and spreading easily through hospitals in the Middle East (and South Korea) (see Ziad Memish: Two MERS-CoV Hospital Super Spreading Studies).

A year ago we looked at an editorial in Journal of Epidemiology & Global Health on the importance of continued healthcare preparedness and surveillance (see Al-Tawfiq & Memish On Recurrent MERS-CoV Transmission in Saudi Arabia), with an emphasis on identifying asymptomatic carriers.

Whether MERS-CoV will re-emerge as a global health threat remains unknown, but it continues to circulate and evolve - largely out of our view - on both the Arabian Peninsula and in Africa.

Which makes it very much worth our attention.

USDA & Texas Announce 2nd New World Screwworm Detection

2026-06-07T08:13:15.618-04:00

Credit USDA

#19,192

Three days ago we saw the USDA Confirm the Presence of New World Screwworm (NWS) in the United States (Texas) for the first time since the 1960s. The NWS is a parasitic fly that lays its eggs in the open wounds of warm-blooded animals (often cattle and deer, but occasionally humans and pets).

Unlike most fly maggots, NWS larva consume and burrow into living tissue, causing substantial morbidity and mortality. (See ASM 2025 Review New World Screwworm: Rise, Fall and Resurgence).

Not unexpectedly, this weekend we are learning of a 2nd case, found in a calf a little more than 5 miles away from the first case.

Although the risk to public health is extremely low, this agricultural pest can be devastating for the cattle industry.

The Texas Governor's office has officially declared two counties ( Zavala & Uvalde) as disaster areas, and has committed the full resources of the state to combat the threat.

Governor Abbott Deploys State Resources To Combat New World Screwworm

June 5, 2026 | Austin, Texas | Press Release

Issues Disaster Declaration for Zavala and Uvalde Counties

Governor Greg Abbott today received a briefing and updated Texans on the state’s response following confirmation of a New World Screwworm (NWS) detection in Texas. The Governor also issued a disaster declaration for Zavala and Uvalde Counties.

“I am issuing an updated statewide disaster declaration to make two things very clear,” said Governor Abbott. “First, I authorize the use of all available resources of state government to respond to this disaster and reassign resources from across the state as needed to address NWS. Second, I am making all state personnel available to accelerate the movement of sterile flies into Texas and the construction of the new sterile screwworm production facility in Edinburg. We have eradicated this pest before, and we will do it again.”

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Excerpts from the USDA's announcement follow:

Animal Health Officials Respond to Second Detection of New World Screwworm in the United States

FOR IMMEDIATE RELEASE
Contact: screwworm@usda.gov

WASHINGTON, D.C., June 5, 2026 — The U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed a second detection of New World screwworm (NWS) after testing a number of suspect cases. The confirmed case was found in a one-month-old calf in Zavala County, Texas, approximately 5.6 miles away from the first confirmed detection. APHIS and our Texas partners continue to collect and test other samples from the surrounding area which have come back negative.

NWS is a serious pest that threatens livestock, pets, wildlife, and, in rare cases, people. The larvae burrow into the living tissue of animals, causing severe wounds, animal suffering, and significant economic losses.

“USDA has responded expediently with respect to this second detection, demonstrating our utmost preparedness. This second detection is within the established movement control zone and enhanced sterile insect dispersal area.” said Dudley Hoskins, Under Secretary for Marketing and Regulatory Programs. “Many models projected this pest would reach the United States last year, but thanks to USDA’s phenomenal work and our cooperation with state, federal, and industry partners, we’ve held it off until now—when we are far more prepared to respond. USDA has not wasted any time in this fight, we have defeated New World screwworm before, and we will do it again."

USDA Strike Team and Rapid Deployment Capacity

An APHIS strike team is already on-site in Texas. This team includes veterinary medical officers and animal health technicians – experienced experts who serve as USDA’s boots on the ground response force. APHIS is fully positioned to surge additional trained personnel as needed.

The National Veterinary Services Laboratories (NVSL) has deployed an entomologist to the USDA Agricultural Research Service laboratory in Kerrville, Texas, to expedite confirmation processes by positioning NVSL diagnostic assets in the area.

APHIS has also deployed two dedicated NWS response cargo trailers. Each 24-foot trailer serves as a mobile preparedness and field operations center. Once unloaded, the trailers convert into operational and laboratory space, providing USDA personnel with the equipment and environment necessary to mount a rapid, efficient response.

Treatment Resources and Supplies

The U.S. Food and Drug Administration has issued emergency use authorizations for several NWS treatments for different species. Currently, there are treatments available to support cattle, horses, swine, goats, captive exotic animals, and wildlife.

The National Veterinary Stockpile is actively procuring additional tools to treat and prevent NWS. USDA is working with federal and regulatory partners, and within federal purchasing processes, to secure more treatment options that are flexible, safe, and effective.

The National Veterinary Stockpile has relocated NWS treatment supplies to Texas to better support affected producers in the infested zone. If you or anyone you know needs access to these treatment supplies, they are now available and can be obtained by reaching out directly to the Texas Animal Health Commission (TAHC).

Intensified Sterile Fly Operations

As part of the established NWS eradication strategy, USDA began releasing sterile flies over the area on June 4. These missions will disperse 2 million sterile screwworms twice a week to disrupt the pest’s lifecycle.

In addition to aerial releases, USDA is shipping another 4 million sterile flies per week to Texas. These will be deployed using 24 ground release chambers, strategically placed in and around the detection zone to maximize impact.

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WHO Influenza at the human-animal interface (May 8th): 10 Novel Flu Detections In Humans

2026-06-07T07:20:35.097-04:00

#19,191

The WHO has released an update (dated May 8th, but only recently posted) of 10 human infections with novel flu reported between April 1st and May 8th, which includes:

3 - A(H5N1) cases (3 Cambodia, 1 Bangladesh, & India)
1 - A(H5N6) case reported by China
5 - A(H9N2) cases reported by China
1 - A(H1N2)v case reported by the United States

Of note, today's report brings the total number of lab-confirmed of human H5N1 cases since 2003 to 1000 (with 47.9% fatal). The actual number of cases is believed much higher.

While some of today's case reports provide more detail than others, it appears that at least 3 of the 4 H5Nx cases in this update experienced delays in diagnosis.

The child in Bangladesh was hospitalized on March 29th - diagnosed with measles with bronchopneumonia - but only tested positive for H5N1 3 weeks later (Apr 20th).
The fatal H5N1 case in Cambodia was hospitalized on April 16th, but was only confirmed H5 positive on April 21st (died on the 22nd).
The child from West Bengal, India was admitted to the hospital for fever and cough on 19 March and discharged on 23 March. While no exact testing date is provided, India notified WHO on March 27th.

As we've discussed previously (see here, here, here, and here), it takes a certain amount of luck for novel flu infections to be detected, properly treated, and then reported to the relevant health authorities.

Patients may present with mild or atypical symptoms, and sample collecting and laboratory testing are not always 100% reliable. Some will never be tested, and many cases will undoubtedly go unreported.

I've reproduced the summary, and some excerpts on individual cases, below. I'll have a bit more after the break.

Influenza at the human-animal interface
Summary and risk assessment, from 1 April to 8 May 20261
• New human cases2: From 1 April to 8 May 2026, based on reporting date, detections of influenza A(H5N1) in three humans, influenza A(H5N6) in one human, influenza A(H9N2) in five humans, and influenza A(H1N2) variant ((H1N2)v) virus in one human were reported officially

.• Circulation of influenza viruses with zoonotic potential in animals: High pathogenicity avian influenza (HPAI) events in poultry and non-poultry animal species continue to be reported to the World Organisation for Animal Health (WOAH).3 The Food and Agriculture Organization of the United Nations (FAO) also provides a global update on avian influenza viruses with pandemi cpotential.4 Additionally, low pathogenicity avian influenza viruses as well as swine influenza viruses continue to circulate in animal populations.
• Risk assessment5: Sustained human to human transmission has not been reported associated with the above-mentioned human infection events. Based on information available at the time of this risk assessment update, the overall public health risk from currently known influenza A viruses detected at the human-animal interface has not changed and remains low. At present,these viruses are not thought to be capable of sustained human-to-human transmission,although this could change as they evolve. Although human infections with viruses of animal origin are infrequent, they are not unexpected at the human-animal interface.
• IHR compliance6: This includes any influenza A virus that has demonstrated the capacity to infect a human and its haemagglutinin (HA) gene (or protein) is not a mutated form of those, i.e. A(H1)or A(H3), circulating widely in the human population. Information from these notifications is critical to inform risk assessments for influenza at the human-animal interface.

(SNIP)

Avian influenza viruses in humans A(H5N1), Bangladesh
On 23 April 2026, Bangladesh notified WHO of one laboratory-confirmed human case of avian influenza A(H5) infection in a child from Sylhet Division. The patient developed fever and cough on 27 March 2026 and was admitted to hospital on 28 March with a clinical diagnosis of measles with bronchopneumonia.

As part of hospital-based influenza surveillance, a sample was collected on 29 March and received by the Institute of Epidemiology, Disease Control and Research(IEDCR) on 20 April. The sample tested positive for influenza A(H5N1) on the same day by real-time reverse transcription polymerase chain reaction (RT-PCR). The patient was discharged on 30 March. No additional cases were reported among identified contacts. Epidemiological investigations identified exposure to household poultry.

This is the second laboratory-confirmed human case of avian influenza A(H5N1) reported in Bangladesh in 2026.

A(H5N1), Cambodia
On 22 April 2026, Cambodia notified WHO of one laboratory-confirmed human case of avian influenza A(H5) infection in a 66-year-old woman with comorbidities from Svay Rieng province. The patient developed symptoms on 15 April 2026 and was admitted to district hospital on 16 April and provincial hospital the next day.

As part of severe acute respiratory infection surveillance, a sample was collected on 17 April and received by the National Institute of Public Health on 21 April. The sample tested positive for influenza A(H5N1) on the same day by real-time RT-PCR, and the result was confirmed by Institut Pasteur du Cambodge on 22 April. The patient died on 22 April. No additional cases were reported among 15 identified contacts. Epidemiological investigations identified exposure to sick and dead household chickens prior to illness onset.

A(H5N1), India

On 27 March 2026, India notified WHO of one laboratory-confirmed human case of avian influenza A(H5N1) infection in a child from West Bengal state. The patient developed fever and cough and was admitted to hospital on 19 March. The patient was discharged on 23 March.
Laboratory testing at the Indian Council of Medical Research (ICMR) National Institute of Virology in Pune confirmed influenza A(H5N1). Genomic sequencing identified the virus as belonging to clade 2.3.2.1a, closely related to strains previously reported from Bangladesh and India in 2025. No additional cases were reported among identified contacts. Epidemiological investigations identified likely indirect exposure to poultry.This is the first laboratory-confirmed human case of avian influenza A(H5N1) reported in India in 2026.

A(H5N6), China
On 29 April 2026, China notified WHO of one laboratory-confirmed human case of avian influenza A(H5N6) infection in a 55-year-old female with comorbidities from Chongqing Municipality. She had onset of symptoms on 16 April 2026 and was hospitalized on 23 April with severe pneumonia. The patient died on 3 May 2026. She had slaughtered and prepared poultry prior to onset of symptoms. Environmental samples collected from the food preparation tools at the patient’s residence tested positive for influenza A(H5). No further cases were detected among contacts of the patient.This is the first laboratory-confirmed human case of infection with an A(H5N6) virus detected since 2024.

(SNIP)

A(H9N2), China
Between 7 April and 6 May 2026, China notified WHO of five laboratory-confirmed cases of A(H9N2)virus infection.

The first case had comorbidities and developed severe pneumonia. All the cases except the child from Jiangxi had exposure to live bird markets or household birds. Samples from environments associated with the likely area of exposure of some of these cases tested positive for A(H9) viruses. No further cases were detected among contacts of these cases.

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As always, the WHO spends a good deal of time imploring member nations to abide by the 2005 IHR regulations which require prompt notification of all human infections caused by novel flu subtypes.

It is critical that these influenza viruses from animals or from humans are fully characterized inappropriate animal or human health influenza reference laboratories. Under WHO’s Pandemic Influenza Preparedness (PIP) Framework, Member States are expected to share influenza viruses with pandemic potential on a timely basis15 with a WHO Collaborating Centre for influenza of GISRS. The viruses are used by the public health laboratories to assess the risk of pandemic influenza and to develop candidate vaccine viruses.

But, according to a report 3 years ago (see Lancet Preprint: National Surveillance for Novel Diseases - A Systematic Analysis of 195 Countries), many member nations still lack the capability to fully investigate cases.

While none of these novel flu viruses currently show signs of spreading efficiently between humans, the general consensus is the next pandemic isn't a matter of `if', only a matter of `when' (see BMJ Global: Historical Trends Demonstrate a Pattern of Increasingly Frequent & Severe Zoonotic Spillover Events).

The only real question is; will we be ready when it comes.

CDC MMWR: Modeled Scenario Projections for the Ebola Disease Outbreak Caused by Bundibugyo Virus, 2026

2026-06-06T05:56:40.932-04:00

“All models are wrong, but some models are useful.” George E. P. Box (18 October 1919 – 28 March 2013) - Professor Emeritus of Statistics at the University of Wisconsin

#19,190

Late yesterday afternoon the CDC held an update (see transcript & video) on the the Ebola virus outbreak in Central Africa, focusing specifically on 3 new reports published Friday in the CDC's MMWR.

The first is an Assessment of Risk to the U.S. Population from the Ebola Disease Outbreak Caused by Bundibugyo Virus, 2026 which finds `. . . the risk posed by this ongoing outbreak to the U.S. population during the next 3 months as low.'

The second is Notes from the Field: Outbreak of Ebola Disease Caused by Bundibugyo Virus — Democratic Republic of the Congo and Uganda, May 2026 which reports `The scope of the outbreak is likely larger than that represented by available data and might prove challenging to contain and control.'

The third report, however - which modeled a variety of possible scenarios for the Ebola Outbreak - was the primary topic of discussion during this presentation.

As with all such models, this isn't a prediction of what will be, only what might be, if certain things aren't done to prevent it.

Based on the following comment from Dr. Pillai during the teleconference, the example given in the summary (70% of cases isolated in 1st 48 hours) doesn't currently appear to be happening:

Dr. Pillai
Currently, the situation is very fluid, and while the numbers are not completely known, based on the trajectory of the outbreak and the rapid extension into multiple different health zones over a short period of time, this appears to be in one of the lower end of the percentage of individuals that are being detected and isolated.

The range of outcomes - based heavily on success in identifying and isolating cases - is depicted in the following chart. If the success rate is < 50%, the risks of seeing 20,000+ cases over the next 3 months rises markedly.

First, some excerpts from the report, after which I'll have a bit more.

Modeled Scenario Projections for the Ebola Disease Outbreak Caused by Bundibugyo Virus, 2026
Early Release / June 5, 2026 / 75

Eric Q. Mooring, ScD1,2; William T. Koval, PhD1; Isobel Routledge, PhD3; Inga Holmdahl, PhD4; Guido España, PhD1; Rebecca Kahn, PhD4; Beau B. Bruce, MD, PhD1

Summary

What is already known about this topic?

An outbreak of Bundibugyo virus disease (BVD), a type of Ebola disease, is currently ongoing, centered in the Ituri province of the Democratic Republic of the Congo (DRC).

What is added by this report?

CDC used a transmission model to project outbreak growth over 3 months, by using different assumptions about the number of deaths as of May 24, 2026, and by varying the percentages of persons with BVD who are successfully identified and isolated to prevent ongoing transmission. Assuming 50 cumulative deaths as of May 24, 2026, if 70% of patients were to enter isolation, only approximately one in 20 simulations projected an outbreak exceeding 10,000 cases within 3 months.

What are the implications for public health practice?

Large-scale, rapid public health action is needed to control the current outbreak, already the largest known BVD outbreak, from becoming one of the largest Ebola epidemics in history.

(SNIP)

Outbreak Size Projections and Inferred Spillover Date by Assumed Number of Deaths

Assuming 50 deaths. The model calibrated to 50 deaths estimated that the spillover event that triggered this outbreak most likely occurred on approximately February 19, 2026 (interquartile interval [IQI] = February 1–March 8). Assuming that 20% of infected persons were successfully isolated beginning May 24, 2026, projections showed ≥20,000 cumulative cases in 65% of simulations, ≥10,000 cumulative cases in 85% of simulations, and ≥4,000 cumulative deaths in 69% of simulations (Figure).

Even with 50% of infected persons isolated, many simulations still projected these numbers of cases but were less likely to occur (17% of simulations projected ≥20,000 cases and 22% projected ≥4,000 deaths). At 70% isolation, projected outbreaks were much more likely to be smaller, but still of substantial size, with 94% of simulations projecting <10,000 cases and only 1% projecting ≥20,000 cases; similarly, at this isolation level, 90% of simulations projected <2,000 deaths and only 3% projected ≥4,000 deaths. Re declined proportional to the percentage of infected persons successfully isolated (Supplementary Figure 1).

Assuming 100 deaths. Assuming 100 cumulative deaths as of May 24, 2026, the inferred median spillover date was February 8, 2026 (IQI = January 21–February 27). Very large outbreaks were likely in the scenario in which only 20% of patients were isolated (76% of simulations projected ≥20,000 cases and 87% projected ≥4,000 deaths). In the scenario in which 70% of infected persons were isolated, 73% of simulations projected <2,000 cumulative deaths by August 22, 2026, and 10% projected ≥4,000 deaths (Supplementary Figure 2).

Assuming 200 deaths. Assuming 200 deaths by May 24, 2026, the calibrated model inferred a median spillover date of January 29, 2026 (IQI = January 9–February 18). The earlier spillover date would have generated a larger outbreak by the time interventions began; thus, even with 70% of infected persons isolated, 42% of simulations projected ≥10,000 cases by August 22, 2026.
Sensitivity to Basic Reproductive Number

Simulated outbreaks with R0 values higher than the median R0 typically reached ≥10,000 cumulative cases and ≥2,000 cumulative deaths by August 22, 2026, in scenarios with ≤50% isolation, even assuming only 50 cumulative deaths by May 24. In the scenario with 70% of infected persons isolated and 50 assumed deaths by May 24, 2026, no simulations projected ≥2,000 deaths when R0 values were lower than the median R0, but 20% of simulations projected ≥2,000 deaths when R0 values exceeded the median (Supplementary Figure 3).

(SNIP)

The high probability of a large outbreak over a 3-month period primarily results from the large size of the outbreak at the time it was initially confirmed. This analysis did not provide evidence that R0 for this outbreak is unusually large.† Time between Ebola outbreak onset and detection is positively correlated with overall outbreak size and duration (4).

CDC’s assessment that the risk to the general U.S. population is low (5) is not changed by this analysis. Despite the unprecedented size of the 2014–2016 West Africa Ebola epidemic, only two Ebola transmission events occurred in the United States. Those two infected persons were health care workers caring for a patient with Ebola who had traveled to the United States before enhanced screening, risk assessment, and health education measures were implemented at U.S. ports of entry (6). Both persons infected in the United States recovered.

(Continue . . . )

All three MMWR reports are worth reading in their entirety, and the video presentation (21 minutes) is very much worth watching.

While conditions could change, right now the DRC and surrounding countries appear to be on a trajectory that could eventually equal or even exceed that seen during the 2014-2016 West African Ebola Outbreak (28K cases, 11K deaths).

But, as they say, `If you've seen one epidemic . . . you've seen one epidemic.' The Bundibugyo virus is a different threat than Ebola Zaire, and the conditions in the DRC, Uganda, and South Sudan differ as well.

For now, this is 99% a regional threat. Exported cases are a possibility, but large outbreaks in places like Europe or North America - which are far better prepared to deal with this virus - are unlikely.

But all of this assumes that reasonable containment efforts are made - or even possible - at ground zero. Long chains of human-to-human transmission are problematic with any zoonotic virus, as it increases the chances that the virus will better adapt to a human host.

Which makes it very much worth our while to do whatever we can to help bring this outbreak under control.

Sooner, rather than later.

FluView Week #20: EOY Review of Increased Detection of Oseltamivir Resistant H1N1 Viruses

2026-06-05T06:33:35.426-04:00

Abrupt rise in Oseltamivir resistance in Catalonia, Spain - fall 2025

#19,189

For the past 3 years we've been following sporadic reports of `reduced susceptibility' of the seasonal H1N1 flu virus to the antiviral drug oseltamivir (aka `Tamiflu') around the globe (see EID Journal: Multicountry Spread of Influenza A(H1N1)pdm09 Viruses with Reduced Oseltamivir Inhibition, May 2023–February 2024).

While concerning, these reports indicated reduced inhibition - not complete failure - and its incidence has been modest; typically in the low single digits.

The main culprit in all of this has been an increase in the S247N mutation (often combined with I223V), which can reduce the effectiveness of oseltamivir 7 to 16 fold.

Less common, but far more impactful, is the H275Y mutation, which can effectively render oseltamivir useless. This was the cause of the `Tamiflu failure' of 2008, which temporarily forced the CDC to change their flu treatment guidelines.

Luckily, the arrival of a new, and still susceptible pandemic H1N1 virus in 2009 granted oseltamivir an unexpected reprieve, but since then we've kept a close eye out for any genetic changes that could affect its effectiveness.

Last summer, in Virus Research: A 15-year Study of Neuraminidase Mutations and the Increasing of S247N Mutation in Spain, we looked at a study that found a sharp increase in detections of the S247N mutation beginning in 2024.

Highlights
• In a landscape of a very narrow arsenal of influenza antivirals, resistance mutations are a significant threat.

• Resistance mutations were present in 0.5-5% in A and B influenza viruses during the last 15 years.

• However, S247N resistance mutation in the NA gene sharply increased during 2023-2024 season.

• While this mutation does not confer strong resistance by itself, their fixation could increase the risk of resistance in the future if other resistance mutations appears or get fixed together with it

Over the 2025-2026 flu season we've continued to see scattered reports of resistance, including Taiwan's CDC reported that 6.5% of the H1N1 viruses characterized in 2025 showed signs of oseltamivir resistance, and China: National Influenza Center Reporting Increased Oseltamivir Resistance in Seasonal H1N1.

As for detections in the United States, as we saw last February, over the entire 2024-2025 flu season - out of 1697 H1N1 viruses tested - only one carried the NA-I223V and NA-S247N amino acid substitutions.

And reassuringly, during the first 13 weeks of the 2025-2026 flu season (Oct - Dec) the CDC reported zero elevated resistance among the first 193 H1N1 viruses tested (see screenshot from FluView Wk 53).

But by the end of February, 2026 (FluView Week 7), things had begun to change. Based now on 517 H1N1 isolates tested since October 2026 - the CDC reported 10 viruses with reduced susceptibility and 4 with highly reduced inhibition.

Four A(H1N1)pdm09 viruses had NA-H275Y amino acid substitution conferring highly reduced inhibition by oseltamivir and peramivir. Ten A(H1N1)pdm09 viruses had amino acid substitutions NA-I223V and NA-S247N and showed reduced inhibition by oseltamivir. Two B viruses had amino acid substitution NA- M464T and showed reduced inhibition by peramivir.

Last Friday the CDC published their last full FluView report of the 2025-2026 flu season (week 20), which contained the following brief update on oseltamivir resistant viruses.

Nine A(H1N1)pdm09 viruses had NA-H275Y amino acid substitution conferring highly reduced inhibition by oseltamivir and peramivir. Nineteen A(H1N1)pdm09 viruses had amino acid substitutions NA-I223V and NA-S247N and showed reduced inhibition by oseltamivir. One A(H1N1)pdm09 virus had amino acid substitutions NA-I223T and NA-S247N and showed reduced inhibition by oseltamivir. Two A(H3N2) viruses had amino acid substitution NA-E119V conferring highly reduced inhibition by oseltamivir. Three B viruses had amino acid substitution NA-M464T and showed reduced inhibition by peramivir.

While the number of S247N+I223V mutations remains low (2.1%), this is more than a 35-fold increase over the previous year, making this a trend well worth following.

The incidence of the far more impactful H275Y mutation (1%) remains about average, but there are concerns that the stacking of H275Y with either I223V or S247N could greatly enhance its impact.

None of this is to suggest we are on the verge of another antiviral crisis, only that we continue to see some concerning trends. And given the gaps in global influenza surveillance and reporting, we are only seeing part of the picture.

As we are so frequently reminded - evolution never stops - and while our current antiviral armamentarium remains effective against seasonal H1N1, the events of 2008 reminds us how quickly that can change.

Stay tuned.

USDA: USDA Confirms Presence of New World Screwworm in the United States

2026-06-04T06:41:57.527-04:00

#19,188

The New World Screwworm (NWS aka Cochliomyia hominivorax) - which was eliminated in the United States during the 1960s - is a flesh-eating parasitic fly that lays its eggs in the open wounds of warm-blooded animals (often cattle and deer, but occasionally humans).

Unlike most fly maggots, which feed on dead tissue, NWS larva consume and burrow into live tissue, causing substantial morbidity and mortality. (See ASM 2025 Review New World Screwworm: Rise, Fall and Resurgence).

During the 1980s, eradication efforts - primarily utilizing the Sterile Insect Technique (SIT) - expanded NWS elimination southward through Mexico and Central America, to the Darien Gap in Panama where for many years (starting in 1996) the line was held.

But in 2023, the number of screwworm detections in Panama surged from a few dozen to thousands, and the infestation began moving northward again. While likely due to a myriad of reasons - including climate change and human migration - supply chain issues during the COVID pandemic is often cited as a factor.

Since then, the NWS has been moving north steadily, and has been reported getting closer to the U.S./Mexico border in recent months. In August of last year, the HHS reported a Singular Traveler-Associated New World Screwworm Case.

The USDA has produced its own projections of the economic impact of NWS (in 2024), which finds it could cost Texas farmers nearly 2 billion dollars a year.

Not unexpectedly, last night the USDA announced the first detection of NWS on a farm in Southern Texas. While this is not a big public health concern, should it spread widely, it could prove quite costly to the cattle industry.

Last night's announcement focuses primarily on reassuring the public (about food safety, and that authorities are responding aggressively). While serious, for now this remains a single detected incursion; not evidence of established transmission within the United States.

First the announcement from the USDA (h/t to Sharon Sanders on FT for the head's up), after which I'll have a bit more.

USDA Confirms Presence of New World Screwworm in the United States

Contact: aphispress@usda.gov

Animal Health Officials Working Quickly to Protect U.S. Livestock and Wildlife

WASHINGTON, DC, JUNE 03, 2026 – The U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the detection of a New World screwworm (NWS) in a bovine in Zavala County, Texas. NWS is a serious pest that affects livestock, pets, wildlife, and less commonly, people and birds. NWS larvae (maggots) burrow into the flesh of living animals, causing serious damage to livestock and economic losses.

The affected animal is a 3-week-old calf and larvae were identified in its umbilical area. To date, there have been no further detections.

“All models showed New World Screwworm entering the country in 2025; however, thanks to the hard work across the entire Trump administration and our industry, state, and local partners, we were able to buy time for this moment. Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action,” said Dudley Hoskins, Under Secretary for Marketing and Regulatory Programs. “USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico. The United States has defeated this pest before, and we will do it again.”

USDA and Texas officials are taking immediate action to contain and eradicate NWS from the United States, following the strategies and actions outlined in the NWS Response Playbook. This includes:

Forming a unified Incident Command Team with the Texas Animal Health Commission and deploying response personnel to the area;
Establishing a 20 km infested zone around the detection and implementing quarantines, movement controls, and surveillance in this area;
Expediting targeted release of sterile NWS flies by immediately deploying ground release chambers in the area, in addition to the 4 million sterile flies per week already being released aerially in the area;
Increasing trapping for NWS flies along the border and just outside of the dispersal area;
Implementing NWS surveillance and management strategies in wildlife; and
Conducting targeted outreach in the local area.
Additionally, USDA’s National Veterinary Stockpile stands ready to assist, and will provide resources including treatments, equipment, and logistics support the response as needed.

USDA will continue to work with state departments of agriculture, animal health officials, industry, and producers to mitigate economic impacts of restrictions as much as possible, including negotiating with our trading partners to regionalize any trade restrictions on live animals, limiting them to defined geographic areas.

NWS maggots can infest livestock and other warm-blooded animals, including in rare cases people. They most often enter an animal through an open wound and feed on the animal’s living flesh.

USDA urges residents in the area to check their pets and livestock for signs of NWS. Look for draining or enlarging wounds and signs of discomfort. Also look for screwworm larvae (maggots) and eggs in or around body openings, such as the nose, ears, and genitalia or the navel of newborn animals. If you suspect your animal is infected with screwworm, contact your state animal health official or USDA area veterinarian in charge immediately.

While not common in people, if you notice a suspicious lesion on your body or suspect you may have contracted screwworm, seek immediate medical attention.

The U.S. food supply is safe. Screwworms do not infest meat, fruits, vegetables, or other food sources. USDA’s Food Safety and Inspection Service (FSIS) ensures that the nation’s commercial supply of meat, poultry, and egg products is safe and properly labeled. Under the Federal Meat Inspection Act (FMIA), FSIS inspection personnel must inspect all eligible animal species unless they are exempt or covered by a state inspection program.

Any evidence of screwworm infestation in an animal would be identified during these inspections, and any contaminated product from an affected animal would not be allowed to enter the food supply.

For more than a year, USDA has led a unified response to NWS. As the lead coordinating agency, USDA has deployed advanced surveillance systems and supported robust cross-border response efforts in Mexico and Central America to combat the pest and push NWS away from the United States. These efforts have bought time for USDA to increase domestic preparedness efforts.

Learn more about New World screwworm at Screwworm.gov.

All this comes at a particularly bad time, since U.S. cattle inventories are already at their lowest level in decades (due to prolonged droughts and high feed costs), and beef prices are at record highs.

As we've seen previously, the introduction (or reintroduction) of agricultural and human diseases can be difficult to contain. A few examples include:

the introduction and spread of West Nile Virus in 1999
the return of Dengue to South Florida after 7 decades
the post-2000-elimination resurgence of Measles in the U.S. and Canada
the expansion of Lyme disease across the nation
and the inexorable spread of Chronic Wasting Disease in North American cervids

The good news is the USDA has known this day was coming, and has been actively preparing for it. Last April, the USDA released an Updated New World Screwworm Response Playbook, and in January announced the Completion of Sterile Fly Dispersal Facility in Texas.

With a little luck, this breach can be contained.

But as long as the NWS continues to circulate in Mexico, future incursions are all but inevitable. And with all such border interdictions, the defender must succeed 100% time, while the invader only has to succeed once.

Preprint: Increased burden of influenza A/H1N1pdm09 in older adults following the COVID-19 pandemic

2026-06-03T07:30:40.845-04:00

#19,187

If there is one constant with influenza A viruses, it is that they are constantly changing; meaning that things that we may have assumed to be true for years or even decades can abruptly change.

One such `truism' has been that H1N1 viruses pose more of a risk to younger individuals - those born after the 1957 H2N2 pandemic emerged - than to the elderly (see PLoS Path.: Childhood Immune Imprinting to Influenza A).

While older individuals weren't immune to H1N1, they have tended to be less susceptible to infection - and typically saw milder disease - than from the H3N2 subtype.

At least - according to a preprint published last week - until 2022, when a new clade of H1N1 emerged (6B.1A.5a.2a) after the COVID-19 induced lull, which appears to have become more impactful on the elderly.

Although it was overshadowed by the outbreaks of early May (hantavirus & Ebola), the JID reported a similar finding (see Effects of Age and Birth Cohort on Influenza A Virus Subtype-Specific Hospitalization Rates, United States, 2010–2025) in late April.

Assuming these reports are correct, the notion that the elderly might enjoy a bit of a respite during H1N1 centric flu seasons may no longer be true, and that could substantially increase the burden on healthcare facilities.

An additional caveat: it has not been established whether (or how strongly) this pattern will persist as H1N1 continues to evolve. Clade 5a.2a has already been largely replaced by newer subclades (see week 20 FluView), so ongoing surveillance and analysis is needed.

First, the link and some excerpts from the preprint, but the full report is very much worth reading.

Increased burden of influenza A/H1N1pdm09 in older adults following the COVID-19 pandemic
Simon P. J. de Jong, Colin A. Russell
doi: https://doi.org/10.64898/2026.05.20.26353664
This article is a preprint and has not been peer-reviewed

Preview PDF

Abstract

Of the two influenza A virus (IAV) subtypes circulating endemically in humans, A/H3N2 and A/H1N1pdm09, A/H3N2 has historically been the dominant driver of disease burden in older adults. Based on an analysis of publicly available global surveillance data from 2015 to 2025 (>300,000 subtyped, age-stratified infections), we report a substantially increased contribution of A/H1N1pdm09 to influenza morbidity in older adults since approximately 2022.

Birth cohort-stratified analyses suggest elevated A/H1N1pdm09 burden among individuals born before 1955-1959, consistent with erosion of pre-existing immunity originally generated by exposure to historical A/H1N1 strains. Pooled estimates across datasets and analytical approaches indicate the increase in A/H1N1pdm09 burden rises with earlier birth year, ranging from 1.22-fold (95% CI 1.08-1.37) for the 1955-1959 birth cohort to 3.10-fold (95% CI 2.58-3.72) for the 1930-1934 cohort. These findings point to a substantial rise in the overall influenza burden among the most vulnerable age groups, with implications for vaccine policy, clinical management, and public health planning.

Main text

Older adults are at markedly elevated risk of severe outcomes from influenza. Of the two influenza A virus (IAV) subtypes currently circulating in humans, A/H3N2 and A/H1N1pdm09, A/H3N2 has historically disproportionately contributed to influenza burden in older adults1,2. However, emerging evidence suggests possible shifts in this epidemiological landscape. A recent US-based study reported increasing contributions of A/H1N1pdm09 virus infections to influenza hospitalizations among older adults since the COVID-19 pandemic3.

(SNIP)

The apparent increases in A/H1N1pdm09 risk are greatest in the earliest birth cohorts (Fig. 2). This could have substantial clinical and public health implications, as risk of severe influenza disease and mortality increases strongly with age5,6. As such, our results have implications for healthcare capacity planning, with likely substantially elevated acute and post-acute healthcare demand due to influenza compared to a counterfactual in which no immune erosion had occurred. The severity of the 2024/2025 US influenza season potentially reflects the erosion of protection in early birth cohorts3, with adults aged 75 and over experiencing the highest rates of A/H1N1pdm09-associated hospitalization since the 2009 pandemic16.

Vaccines have demonstrated effectiveness against A/H1N1pdm09 among adults aged 65 and over in the post-pandemic period17,18, but new targeted analyses in the earliest birth cohorts, for which estimated increase in burden is greatest (Fig. 2), would be valuable. A potential concern is that individuals whose immunity was shaped predominantly by early-life responses to historical A/H1N1 epitopes may, through repeated boosting of those same responses, lack immunity to epitopes on strains circulating since 2022, leaving them with little cross-reactive protection to recall upon vaccination or infection. These uncertainties notwithstanding, the elevated A/H1N1pdm09 risk suggested here further strengthens the case for vaccination in these birth cohorts and has implications for vaccination strategies, including the value and cost-effectiveness of enhanced formulations which have demonstrated superior immunogenicity and effectiveness in older adults19.

The US and Brazil hospitalization data indicate increased burden of severe disease due to A/H1N1pdm09, but whether this is due to changes in infection risk and/or changes in clinical severity warrants further investigation, particularly given that A/H1N1pdm09 was associated with relatively severe outcomes among hospitalized adults before the COVID-19 pandemic20,21.

Our analyses rely on observational data and are susceptible to reporting biases; however, consistency across four surveillance systems with distinct ascertainment mechanisms and varying analysis methods makes a surveillance artifact implausible. Replication with additional age- and subtype-resolved surveillance data would further substantiate our findings.

Together, our results indicate that the earliest birth cohorts, who are the most clinically vulnerable and have historically been considered relatively protected from influenza A/H1N1pdm09, likely now face substantially elevated risk from these viruses.

This carries potential implications for vaccine policy and healthcare capacity planning. Ensuring that surveillance infrastructure captures age- and subtype-resolved influenza data globally will be essential for tracking this shift and quantifying its consequences for the populations most at risk for severe influenza.

(Continue . . . )

We tend to think that next year's seasonal flu will be pretty much like last year's, and the year before. But even non-pandemic flu viruses can throw us curves.

In 2008, H1N1 abruptly developed nearly 100% resistance to oseltamivir;

In 2014, we saw a late summer mutation appear in the H3N2 virus (see HAN Advisory On `Drifted’ H3N2 Seasonal F lu Virus) which greatly reduced the effectiveness of that year's flu vaccine.

in 2016, we saw warnings over mutated (D225G) H1N1 viruses in Russia and in Europe (see ECDC Risk Assessment : Reports Of Severe A(H1N1)pdm09 In Europe);

Again in 2025, a drifted (Subclade K) H3N2 emerged which impacted vaccine effectiveness

And while it has had only limited impact so far, we are now watching another slow rise in antiviral resistance in H1N1.

All reasons why we should give seasonal flu the respect it deserves.

CMAJ: Acetaminophen in pregnancy

2026-06-02T06:01:13.835-04:00

Photo Credit – Wikipedia

#19,186

Last September, following a White House announcement suggesting a link between acetaminophen use during pregnancy and rising rates of autism, we looked at a statement from the World Health Organization and other medical stakeholders which pushed back on the theory.

While no drug can claim to be 100% safe in 100% of the people that take it, these OTC pain/fever relievers have long been considered the safest option for both the mother and unborn child.

We've looked at potential drivers of increased autism often over the years, and after genetics, environmental exposures - and increased recognition of those on the spectrum - fevers during pregnancy are frequently cited (see Molecular Psy.: Increased Autism Risk Linked To Prenatal Fever).

While a few studies have claimed a statistical link between acetaminophen use during pregnancy and autism (Link), none have found a causal link, and a large 2024 study found `Acetaminophen use during pregnancy was not associated with children’s risk of autism, ADHD, or intellectual disability in sibling control analysis.'

The concern is: disparaging the only `presumed safe' option to reduce maternal fevers could actually end up increasing the incidence of autism, instead of decreasing it.

We revisited this story last January in The Lancet: Prenatal Paracetamol Exposure and Child Neurodevelopment: A Systematic Review and Meta-Analysis, which incorporated 43 studies (17 of which were combined in the meta-analysis), which reported:

Current evidence does not indicate a clinically important increase in the likelihood of autism spectrum disorder, ADHD, or intellectual disability in children of pregnant individuals who use paracetamol as directed, supporting existing recommendations on its safety.

Additional research is still needed to better understand heavy or prolonged usage, but these findings should be reassuring to anyone who chooses to use these drugs during pregnancy.

Under Implications of all the available evidence, the authors wrote:

Taken together with large-scale sibling-controlled studies from Sweden and Japan published in 2024 and 2025, our findings support the safety of paracetamol when used appropriately during pregnancy. They reinforce the guidance of major professional and regulatory bodies, including the American College of Obstetricians and Gynecologists, the Royal College of Obstetricians and Gynaecologists, and the European Medicines Agency, which continue to recommend paracetamol as the first-line analgesic and antipyretic in pregnancy.

Avoiding paracetamol based on inconclusive or biased evidence might increase the risk of maternal fever or untreated pain, both of which can harm pregnancy outcomes. Future research should focus on improving exposure measurement, standardising outcome definitions, and integrating mechanistic and family-based designs to clarify any residual uncertainties.

Admittedly, not a rock solid 100% guarantee of absolute safety; but in life, precious little is.

Weighing in on all of this, yesterday the CMAJ published a brief review on the use of acetaminophen in pregnancy, and they too find that `Current evidence does not indicate a causal link between acetaminophen use in pregnancy and adverse infant outcomes.'

For those looking for a bit more reassurance, I've posted their report below.

Acetaminophen in pregnancy
Jonathan S. Zipursky Rachela Smith and Tali Bogler CMAJ
June 01, 2026
DOI: https://doi.org/10.1503/cmaj.260138
PDF

Acetaminophen is the preferred analgesic and antipyretic agent for pregnant people

More than half of pregnant people use acetaminophen, most commonly for pain.1 Compared with alternatives, acetaminophen is the best studied analgesic and antipyretic in pregnancy and has the most reassuring maternal and fetal safety profiles. Major regulatory and obstetrical organizations support judicious use of acetaminophen as the first-line treatment for fever and pain in pregnancy.2

Studies on the risks of neurodevelopmental disorders related to acetaminophen use in pregnancy have not established causation

Some systematic reviews suggest small associations between prenatal acetaminophen use and autism spectrum disorder and attention-deficit/hyperactivity disorder. However, studies that rigorously control for potential confounders or emphasize sibling-controlled designs have typically found weaker or null associations.3,4 This suggests that unmeasured confounders (e.g., genetic and environmental factors) largely explain the associations with neurodevelopmental disorders.5 Randomized controlled trials have not been conducted, and therefore methodological weaknesses in existing observational studies limit conclusions about causation.

Data on fetal reproductive and endocrine effects show small, inconsistent associations

Results from observational studies linking prenatal acetaminophen use to abnormalities in the male reproductive tract are inconsistent; some studies have demonstrated small associations with cryptorchidism and reduced anogenital distance, while others have not.5 Furthermore, most studies relied on maternal memory of acetaminophen use in pregnancy, raising the potential for recall bias that may increase observed effect sizes or lead to spurious associations.

Untreated maternal fever has been associated with adverse fetal outcomes

Separating the potential effects of acetaminophen from those of the underlying condition is challenging. Treatment of fever in pregnancy is clinically indicated; in some observational studies, maternal fever was linked to increased risks of neurodevelopmental disorders.6 First-trimester fevers have been linked to congenital abnormalities such as neural tube, heart, and oral cleft defects.7

Counselling on acetaminophen use in pregnancy should emphasize a critical approach to interpreting the data

Current evidence does not indicate a causal link between acetaminophen use in pregnancy and adverse infant outcomes. Clear counselling by clinicians about the limitations of existing observational data can reduce unnecessary anxiety or avoidance of appropriate fever and pain treatment in pregnancy.

Preprint: Detection of Anti-H5 Antibodies in People with Exposure to Wild Birds in Northern Canada

2026-06-01T08:10:30.536-04:00

#19,185

Almost exactly 2 years ago - 3 months after the discovery of HPAI H5N1 in U.S. dairy cows - the CDC released the results of their study on Population Immunity to A(H5N1) clade 2.3.3.4b Viruses. They reported:

CDC analyzed sera (blood) collected from people of all ages in all 10 HHS regions. Blood samples were collected during the 2022-2023 and 2021-2022 flu seasons. These samples were challenged with H5N1 virus to see whether there was an antibody reaction.

Data from this study suggest that there is extremely low to no population immunity to clade 2.3.4.4b A(H5N1) viruses in the United States. Antibody levels remained low regardless of whether or not the participants had gotten a seasonal flu vaccination, meaning that seasonal flu vaccination did not produce antibodies to A(H5N1) viruses.

This was in the United States, of course, where exposure to HPAI H5N1 has historically been very low. Over the years we've looked at a number of other seroprevalence studies - particularly in regions with known outbreaks - which have produced slightly different results.

In 2004 (see The Thailand Serological Study) 322 poultry farmers (in provinces where H5N1 had been detected) were tested. Researchers found that "no poultry workers had microneutralization titers >80, whereas 7 (2%) had lower titers that did not meet the WHO definition for seropositivity".
In May of 2009 (see Cambodian Study Finds Rare Asymptomatic H5N1 Infections) we saw a study published in the Journal of Infectious Diseases on more than 600 members of a Cambodian village where 2 human H5N1 cases were detected in 2006. Antibody titers showed that only 1% (7 of 674) of the villagers tested had contracted, and fought off, the H5N1 virus. A figure much lower than many had expected.

In 2012, in H5N1 Seroprevalence Among Jiangsu Province Poultry Workers, we saw a study that found across three locations tested (Gaochun, Jianhu and Gaoyou counties) the percentage of workers testing positive ranged from zero (Gaochun) to 5.38% (95%CI, 2.19%–10.78%) in Gaoyou.

More recently, in 2024's MMWR: Serologic Evidence of Recent Infection with HPAI A(H5) Virus Among Dairy Workers, in a relatively small sampling (n=115) 7% (n=8)` . . . of exposed dairy farm workers in Michigan and Colorado had serologic evidence of infection with HPAI A(H5).'

Not unexpectedly, people with direct exposure to infected poultry or livestock tend to have higher detectable levels of HPAI H5 antibodies than the general population. There are a few caveats to serological tests, including:

They only pick up past infections ( >1-3 wks), and are not designed to detect current infections
Detectable levels of influenza antibodies can wane over time, meaning older or milder exposures might no longer be detectable
Exposure to some subtypes can sometimes produce cross-neutralizing antibodies to another (see EID Journal: A(H5N1) NA Inhibition Antibodies in Healthy Adults after Exposure to Influenza A(H1N1)pdm09).

In other words - while incredibly useful for retrospective investigations - there has always been some degree of ambiguity regarding the results of seroprevalence testing.

All of which brings us to a preprint, published last week, which looks as a small sampling (n=65) of blood samples collected from people (mostly hunters) with exposure to wild birds in Northern Manitoba, Canada.

The authors reports a ` 7.4% (n=5/68) anti-H5 seroreactivity rate among hunters in Northern Canada'. Some of these hunters had exposure to small mammals as well.

The authors list some of the limitations to their study, stating:

The relatively small sample size of the study provides limited power for statistical analyses, and given that the study was conducted in a small region of Manitoba, future larger-scale studies are needed to evaluate how commonly people with exposure to wild birds may be infected by H5N1.
Unfortunately, the durability of the antibody response to H5N1 is unknown, therefore we can only conclude that the five seroreactive individuals have been exposed to the virus at some during their lifetimes, although the durability of antibodies against avian influenza in human populations is unknown. Whether these individuals experienced symptomatic or asymptomatic infections, and whether they would be protected from subsequent re-infection, is also unknown.

I've reproduced the summary and a few excerpts below, but you'll want to follow the link to read this (not-yet peer-reviewed) report in its entirety. I'll have a bit more after the break.

Detection of Anti-H5 Antibodies in People with Exposure to Wild Birds in Northern Canada
Hannah L. Wallace, Morgan Hiebert, Mikayla Hunter, Megan Halbrook, Ryan J. Harrigan, Isaac I. Bogoch, Anne W. Rimoin, Souradet Shaw, Linda Larcombe, Pamela H. Orr, Jason Kindrachuk
doi: https://doi.org/10.64898/2026.05.24.26353994

Posted May 26, 2026.

PDF

Summary
Using a commercially available H5 serology assay, we identified a 7.4% (n=5/68) anti-H5 seroreactivity rate among hunters in Northern Canada. All participants reported close contact with wild birds.
The Study

In August 2025 (three months after the 2025 spring goose hunting season), 68 dried blood spot (DBS) samples with matched questionnaires (Appendix 1) were collected from a northern community in Manitoba, Canada. Recruitment was focused on those > 18 years old who were involved in the hunting of birds and/or preparing them (plucking, butchering, food preparation) for consumption.

Some of the participants were also involved in hunting, trapping and handling of mammals (Table 1). Participants were recruited through social media posts and community posters. Participation was voluntary, and included both local community members as well as individuals who were visiting the community for the upcoming fall goose hunting season. Participants were compensated for their involvement in the study. This study was approved by the University of Manitoba Health Research Ethics Board under study HS26941 (H2025-151).

(SNIP)

Conclusions
This work indicates that people living and/or hunting in northern Manitoba, Canada have been exposed to H5Nx viruses. Knowledge and concerns about H5N1 among study participants was low, indicating a need for more robust and accessible public health information. Future work including sampling a larger number of individuals and performing longitudinal follow-up to determine how antibody levels change over time would be of significant value. Overall, this work adds to the growing body of literature that aims to understand the true extent of spillovers of avian-origin influenza viruses into humans.

(Continue . . . )

This isn't the first time we've looked at the potential increased HPAI risk to hunters (and to hunting dogs). Last February we saw Several States Warn On Contact With Wild Birds/Mammals, and the USDA has warned of the risks for several years.

Of course, hunting isn't the only high risk activity.

In 2024's Mixed Messaging On HPAI Food Safety - we looked at the risks from the slaughtering of live birds and preparation of raw poultry; especially from birds raised at home or purchased from live markets.

There are scores of LBMs (live bird markets) in the United States (see USDA Report 9 More Live Bird Markets Infected With HPAI H5), and millions of families raise, and slaughter, their own backyard poultry.

Sadly, the public appears largely unconvinced of the threat from HPAI (see Two Surveys (UK & U.S.) Illustrating The Public's Lack of Concern Over Avian Flu), which almost certainly provides the virus with more opportunities to spread and evolve.

QJM: Avian Influenza in Humans: Virology, Transmission, and Clinical Priorities

2026-05-31T06:52:19.937-04:00

Credit WHO

#19,184

While there are no signs that avian influenza is spreading in an efficient or sustained manner between humans, there are concerns that some spillover infections are going unrecognized, and each instance provides with virus with another opportunity to adapt to a human host.

Retrospective antibody testing has shown that some infections are either mild, or subclinical (see JAMA Open: Asymptomatic Human Infections With Avian Influenza A(H5N1) Virus Confirmed by Molecular and Serologic Testing).

Although HPAI H5N1 (clade 2.3.4.4b) is currently viewed as the most worrisome avian flu virus, there are many others, including other H5 subclades (2.3.2.1c or 2.3.2.1a), other H5Nx subtypes, H7 viruses, H9N2, H3N8, and H10Nx.

We've also seen reports of atypical presentation (both mild and severe) with avian influenza, along with difficulties in testing some patients, even in a modern hospital setting.

Because of this, we've seen many instances where patients have been hospitalized for days or even weeks before their avian flu infection was finally confirmed. A few examples:

In the fall of 2024, a Missouri man was hospitalized for a week - then released - only to be notified that he had tested positive for H5N1

In June of 2025, we saw a Statement on a Fatal H5N2 Infection In Mexico City, which we would eventually learn, was only detected 2 weeks after the patient had died.

Last April, in Eurosurveillance, we looked at an imported fever/cough case in Italy who initially tested negative for influenza A/B, RSV & COVID, but after a more invasive BAL (Bronchoalveolar lavage), was identified as having H9N2 on the 6th day of his hospitalization.

And 3 weeks ago, the MMWR report on the fatal H5N5 case in Washington State last year repeatedly tested negative for influenza/COVID during the first 6 days of his hospitalization.

While avian flu normally presents as a respiratory infection, we've also seen cases where the symptoms were primarily gastrointestinal, neurological, or subclinical.

In April of 2025 we saw a preliminary report on a neuroinvasive infection in an 8-y.o. girl (see Vietnam: Ho Chi Minh DOH Reports A Rare H5N1 Encephalitis Case In a Child). While her throat and nose swabs tested negative for influenza A, H5N1 was detected in the patient's cerebrospinal fluid.

As noted by infectious experts, this is a rare case in which the A/H5N1 avian influenza virus damages the central nervous system and does not attack the respiratory tract.

All of which brings us to a narrative review - published this week in the QJM - which argues that avian flu is no longer just a `poultry exposure risk', as its many variants continue to expand both their geographic and (avian & mammalian) host ranges around the globe.

The opportunities for spillover into humans have increased markedly over the past few years, which makes its important for clinicians to raise their index of suspicion - particularly during times of known outbreaks - even when dealing with atypical presentations or negative test results.

While this review is `avian flu specific', much of it applies to swine and other novel flu viruses as well. Due to its length, and technical nature, I've only posted some excerpts. Follow the link to read it in its entirety.

Avian Influenza in Humans: Virology, Transmission, and Clinical Priorities
Nitin Gupta , Anna Smielewska , Jan Felix Drexler , Casandra Bulescu , Marta Mora-Rillo , Aleksandra Barac , Pikka Jokelainen , François-Xavier Lescure , Martin P Grobusch , Sotirios Tsiodras ... Show more
QJM: An International Journal of Medicine, hcag138, https://doi.org/10.1093/qjmed/hcag138
Published:29 May 2026 Article history

PDF

Abstract

Avian influenza continues to evolve as a zoonotic threat with important implications for clinical practice and global health preparedness. Sustained circulation in wild birds, repeated spillover into poultry, and an increasing number of infections across diverse mammalian hosts have reshaped exposure pathways and broadened the risk landscape for human infection. For clinicians, this evolving ecology translates into atypical presentations and increased diagnostic uncertainty. Recent global activity has been characterised by widespread animal outbreaks and the emergence of new transmission interfaces, including occupational exposures and livestock-associated events. Human infections remain largely zoonotic and geographically heterogeneous, with patterns influenced by surveillance intensity, exposure context, and healthcare access.

We synthesise current evidence on the virology, transmission, global epidemiology, clinical manifestations, diagnosis, treatment, and prevention of avian influenza in humans. We highlight evolving mammalian adaptation and changing risk interfaces that complicate risk assessment. Improved clinician awareness, early diagnosis, and integrated One Health surveillance remain central to strengthening preparedness for future influenza threats.

(SNIP)

Clinical Presentation and Diagnosis of Avian Influenza in Humans
Human infection with avian influenza viruses spans a broad clinical spectrum, ranging from asymptomatic infection to severe, rapidly progressive multisystem disease (Table 1) [2,56]. Asymptomatic or subclinical infection has increasingly been recognised through serosurveys and occupational surveillance programmes, indicating that mild infections are likely underdetected outside targeted screening settings [57,58].
In a serosurvey of bovine veterinary practitioners in the United States during the 2024 H5 outbreak in dairy cattle, antibodies indicating recent infection were detected in 3 of 150 participants (2%), none of whom reported respiratory or influenza-like symptoms [58]. Similar findings from studies among poultry workers have demonstrated measurable seropositivity in individuals without recognised illness [57].
These observations indicate that reliance on clinically apparent cases may underestimate the true burden of zoonotic infections and lead to overestimation of case fatality rates based solely on detected severe cases.
(SNIP)

Neurological complications, including encephalopathy, encephalitis, seizures, convulsions, and altered consciousness, have been reported in severe H5N1 infection and may occasionally dominate the clinical picture, even in the absence of prominent respiratory disease [69,70].
Human case reports describe acute encephalitis with detectable H5N1 RNA in cerebrospinal fluid, including a child with minimal respiratory symptoms who developed encephalitis complicated by obstructive hydrocephalus, supporting direct central nervous system involvement [71]. Other reported manifestations include diffuse encephalitis, coma, and rapidly progressive neurological deterioration in the setting of severe systemic infection.
Neuropathological and postmortem studies have demonstrated viral antigen and RNA in neurons and glial cells across multiple brain regions, supporting direct neuroinvasion rather than solely secondary inflammatory injury [69]. Experimental studies in ferrets further support this neurotropic potential, showing that H5N1 can invade the brain, often via the olfactory pathway, and may be associated with encephalitis, vasculitis, hemorrhagic lesions, and even subclinical but persistent brain injury [72].

(SNIP)

Conclusion
Avian influenza is ecologically entrenched, globally mobile, and increasingly multi-host. The expansion of H5Nx viruses into previously unafflicted regions, diverse mammalian species, combined with persistent circulation in wild birds and poultry, underscores that the conditions for emergence are continuously present. Apparent epidemiological lulls may reflect surveillance artefacts rather than reduced risk.
In a world where birds migrate, viruses reassort, and agricultural systems are intensified, preparedness, not prediction, remains the most reliable defence. Strengthening One Health surveillance, ensuring rapid clinical recognition, and maintaining flexible medical countermeasures are essential to prevent avian influenza from becoming the next global pandemic. For clinicians worldwide, recognising avian influenza as an evolving zoonotic interface rather than a rare exotic infection will be central to early detection and response.

(Continue . . . )

California: LA County HAN (Health Alert Network) Advisory on Upcoming World Cup

2026-05-29T08:58:20.554-04:00

Credit Wikipedia

#19,183

As we discussed at some length last January (see Public Health Ontario: Hazard Identification and Risk Assessment (HIRA) For the FIFA World Cup 2026 Games in Toronto), this summer 16 cities across 3 North American countries (Canada, Mexico, U.S) will host the 2026 world cup, with over 5 million fans expected to travel to the various venues.

As with all mass gathering events (see Potential Impact of Hajj 2025 & Other Mass Gathering Events On Public Health) there are always public health concerns.

While some of the more exotic diseases (avian flu, MERS-CoV, Ebola, etc.) are often the first threats that come to mind, most infectious illnesses acquired during these mass gathering/migration events are far more common; seasonal flu, COVID, pneumonia, measles, meningococcal disease, mpox, norovirus, and vector borne infections (Zika, CHKV, Dengue, Malaria, Yellow Fever, etc.) (see CDC's Traveler's Health Saudi Arabia).

Not all public health threats will be from infectious diseases; as increased heat-related illnesses, accidents, substance use, and overdoses are also often associated with these types of events.

Accordingly, this week the LA County Department of Public Health released the following HAN Advisory for health care providers on the upcoming World Cup festivities.

Similar advisories will no doubt be issued by other World Cup venues, as local hospitals, EMS units, and public health agencies gear up to provide essential services during these events.

Taiwan Amends Travel Restrictions Due to Ebola Threat

2026-05-29T07:10:23.028-04:00

International Air flights - Credit Wikipedia

#19,182

Two days ago, in ECDC Ebola Update & Individual Country Responses From Canada, U.S. & Taiwan, we looked at recently imposed travel restrictions and protocols due to the central African Ebola outbreak here in the U.S., in Canada, and in Taiwan.

Although the there are long-standing international agreements not to restrict travel and trade during disease outbreaks (see 2005 IHR agreement), as Tip O'Neill famously noted; `. . . all politics is local'.

We saw this adage in action during the opening days of COVID, when much of the advice contained in the WHO's 2019 91-page Influenza NPI guidance document was quickly abandoned by member nations; particularly their recommendations against border closures and travel restrictions.

High-minded ideals (even when backed by science) hold little sway when public officials are forced explain to their constituents why they didn't even try to prevent the entry of a pandemic or epidemic virus.

Citing similar moves by both Canada and the United States, today Taiwan's government has amended their previously announced policy, and have suspended the issuance of entry visas from the DRC and Uganda (with 4 exceptions) for the next 90 days.

While not a huge story in and of itself, this is a reminder of how fluid the Ebola situation is - how concerned governments really are - and how quickly policies may be amended or changed.

As we discussed two days ago, there is no `one-size-fits-all' solution to the Ebola threat, and so we are likely to see a wide range of responses, with varying degrees of success.

Stay tuned.

The full translated announcement follows.

In response to the escalating Ebola outbreak, starting from 00:00 on June 2, 2026, entry into the Democratic Republic of Congo and Uganda will be suspended for 90 days, except for four categories of individuals.

Release Date: 2026-05-29

The Centers for Disease Control (CDC) stated today (May 29) that, according to data released by the WHO as of May 27, 2026, the COVID-19 outbreak continues to expand in the Democratic Republic of Congo (DRC) and Uganda, primarily affecting Ituri, North Kivu, and South Kivu provinces within the DRC. The DRC has reported a cumulative total of 906 cases (223 deaths) and 125 confirmed cases (17 deaths). Uganda has reported a cumulative total of 7 confirmed cases to date, including 1 death. Based on the assessment of the Taiwan Centers for Disease Control (CDC), the Ebola outbreaks in the Democratic Republic of Congo and Uganda are likely to continue to escalate.

In addition to strengthening cross-airport joint prevention and control measures and enhancing port monitoring and interception mechanisms, Taiwan, in order to further reduce the risk of imported cases and referencing practices in the United States and Canada, has jointly discussed with the Ministry of Foreign Affairs and the Bureau of Consular Affairs, the National Immigration Agency of the Ministry of the Interior, and the Civil Aeronautics Administration of the Ministry of Transportation and Communications, and will implement new border epidemic prevention and control measures as follows:

I. Starting from 00:00 on June 2, 2026, the issuance of visas to residents of the Democratic Republic of Congo and Uganda will be suspended; those already issued visas will have their entry temporarily suspended for 90 days. However, the following four categories of individuals will be excluded:

(I) Students who have already obtained admission permission from Taiwan
; (II) Diplomatic and official duties
; (III) Spouses of Taiwanese citizens who are not Taiwanese citizens and their minor children
; (IV) Emergency or humanitarian assistance: such as attending funerals or visiting seriously ill relatives.

II. Taiwanese citizens who have traveled to epidemic areas within 21 days prior to entry, holders of valid Taiwanese residence permits, and those permitted to enter Taiwan are still subject to the measures announced by the Centers for Disease Control and Prevention (CDC) on May 27. They must proactively report to the airport quarantine station upon arrival in Taiwan, where quarantine personnel will issue an "Inbound Passenger Self-Health Management Notice." They must conduct self-health management for 21 days after entry, and follow the requirements of the notice to report their health status. If symptoms appear, they should immediately call the epidemic prevention hotline 1922 for assistance from health authorities.

The CDC explained that the aforementioned control measures will be adjusted in a timely manner based on the latest international epidemic situation and the epidemic prevention risks at Taiwan's borders. The CDC reiterated that the travel epidemic recommendation level for the Democratic Republic of Congo (DRC) and Uganda is Level 3 "Warning," urging the public to avoid all non-essential travel to these countries.

The Taiwan Centers for Disease Control (CDC) reiterates that, to strengthen border quarantine, in addition to enhancing public awareness through airport multimedia electronic billboards, scrolling displays, and signage, it has been making in-flight announcements on all international flights arriving in Taiwan since May 27th. Passengers who have traveled to the Democratic Republic of Congo or Uganda within the past 21 days are urged to proactively report to the quarantine station upon arrival in Taiwan for TOCC and health assessment. Please cooperate with the following quarantine measures:

1. Passengers assessed as having suspected Ebola virus infection symptoms (fever, headache, muscle pain, nausea, vomiting, abdominal pain, diarrhea, or bleeding, etc.) will be immediately transported by ambulance to a contracted hospital for examination, and local health authorities will be coordinated in their prevention and control efforts.

2. Asymptomatic passengers will be issued a "Notice of Self-Health Management for Passengers with Travel History to Ebola-Epidemic Areas." Upon arrival, please cooperate with 21 days of self-health management, keep your phone accessible for contact tracing by health authorities, take your temperature twice daily (morning and evening), and report your health status to the "Public Proactive E-Reporting System." If you experience any of the above symptoms, please call the epidemic prevention hotline 1922 immediately for assistance from the Health Bureau to seek medical attention. Those who do not cooperate with the above measures will be penalized in accordance with the Infectious Disease Prevention and Control Act.

WHO DON Update: Hantavirus outbreak linked to cruise ship travel, Multi-locations

2026-05-29T05:32:31.047-04:00

#19,181

Although the hantavirus outbreak among the passengers and crew of the m/v Hondius has slowed, 3 new cases have been reported over the past 2 weeks, and the isolation, quarantine, and/or monitoring of exposed individuals continues.

While additional hantavirus cases are still possible, a much larger threat has since emerged in Central Africa with the rapidly expanding Bundibugyo virus outbreak in the DRC and Uganda.

Yesterday the WHO released their first formal DON update on the Andes Hantavirus outbreak since May 13th, which adds the 3 latest cases, and reiterates that the global risk level from this outbreak remains low.

Due to its length, I've only posted some excerpts. Follow the link to read it in its entirety.

Hantavirus outbreak linked to cruise ship travel, Multi-locations
28 May 2026

Situation at a glance

This is the fourth Disease Outbreak News report on the Andes hantavirus outbreak linked to cruise ship travel, following the notification to the World Health Organization (WHO) on 2 May 2026 of severe respiratory illness cases aboard M/V Hondius, a cruise ship. Since the last DON was published on 13 May, three additional confirmed cases were reported, from Canada, the Netherlands, and Spain. The previously reported inconclusive case from the United States of America was subsequently determined to be negative following further laboratory testing and has been removed from the total case count. All cases to date have been passengers or crew members on the ship.
As of 27 May, a total of 13 cases, including three deaths, have been reported (case fatality ratio 23%). Eleven cases have been laboratory-confirmed for Andes virus (ANDV) infection, and two are probable cases. Given the long incubation period of up to six weeks, it is not unexpected that cases continue to be reported until the end of the six weeks since last exposure. Through the International Health Regulations (2005) (IHR) channels, National IHR Focal Points (NFPs) have all been informed and are supporting international contact tracing and monitoring efforts. WHO has assessed the risk posed by this event to the global population as low and will continue to monitor the epidemiological situation and update the risk assessment as needed.

(SNIP)

High-risk contacts are being quarantined and monitored by local health authorities either in their respective countries or in the ship’s flag country, the Netherlands, or third countries (Table 1). As of 22 May 2026, more than 600 contacts, including 53% high-risk and 47% low-risk contacts, have been identified across 32 countries, territories and areas, and are either under close monitoring or self-monitoring in line with the updated guidance on management of contacts of Andes virus (ANDV) cases from the MV Hondius cruise ship published on 17 May.

WHO risk assessment

WHO continues to assess the risk for passengers and crew who were onboard the cruise ship as moderate, as individuals exposed prior to the implementation of control measures may still develop illness during the incubation period and should therefore be closely monitored.

The risk at the global level is assessed as low for the following reasons:

Andes virus has demonstrated limited human-to-human transmission in previous outbreaks, typically occurring among close contacts and within household settings, generally requiring prolonged close exposure. Transmission can be contained through early detection, isolation of cases, clinical management, and contact management. However, the ship environment presented an increased risk due to close living quarters, shared indoor spaces, prolonged exposure, and frequent interpersonal interactions, all of which likely facilitated transmission.
Human Pulmonary Syndrome caused by hantaviruses in the Americas, including Andes virus, can have a high case fatality ratio, reaching 40-50%, particularly among elderly individuals and those with co-morbidities. The average age of passengers on board the ship was 65 years old.
Investigations on the travel history and potential exposures of the first case in the Southern Cone subregion of the Americas are ongoing and suggest possible exposure to rodents during recreational activities. Viral sequencing analyses are also ongoing and are comparing the ANDV strain associated with this outbreak with strains circulating in Argentina and Chile, where the disease is enzootic. The preliminary sequencing analysis for the cases indicates a high degree of genetic similarity amongst sequenced cases —showing no more than one single nucleotide polymorphisms difference per individual – which strongly indicates that the outbreak likely arose from a single zoonotic spillover event, or from a very small number of closely related spillover events.[1]
Additional cases may occur among individuals exposed before implementation of containment measures. However, the current response, including quarantine for those who have left the ship and rapid isolation of any new suspect cases and the monitoring of contacts, is expected to limit the risk of further spread.
As there is no specific antiviral treatment for HPS, suspected cases require prompt transfer to an adequately equipped emergency department or intensive care unit, where available, for close monitoring and supportive management to improve chances of recovery. Consequently, for remote areas, rapid transfer to a well-resourced healthcare facility is required, which may be challenging under the current conditions.

For the general public, including people not exposed on board the ship or through close contact with a confirmed case, the overall probability of infection remains low. Current evidence indicates that human-to-human transmission occurs through close and prolonged contact, and can be effectively limited through early detection, isolation of cases, and contact tracing.

(Continue . . . )

JAMA Network Open: Long COVID Persistence and Surveillance Gaps Across 58 US Hospitals

2026-05-28T06:48:56.437-04:00

#19,180

For a variety of economic, political, and societal reasons most of the world's nations have moved towards `normalizing' COVID infection; treating it more as if it were the `flu' or the common `cold'.

Testing outside of the hospital environment is now uncommon, and ICU admissions and deaths are no longer published by 90% of the world's nations.

Although COVID deaths have dropped, the evidence continues to show that COVID infections - and particularly repeated infections - can still take a considerable toll on human health.

While `Long COVID' and PASC (Postacute Sequelae of COVID) are now officially recognized conditions, its presentation is often `messy'; with multiple diffuse - and sometimes conflicting - symptoms.

A few studies of note include:

The Lancet: Long COVID and Risk of Incident Cardiovascular Disease

EID Journal: Thrombotic Events and Stroke in the Year After COVID-19 or Other Acute Respiratory Infection

Nature: Long-term Cardiovascular Outcomes of COVID-19

AHA: COVID-19 May Trigger New-Onset High Blood Pressure

NIH: Study Shows SARS-CoV-2 Infects Coronary Arteries, Increases Plaque Inflammation

EHJ: Accelerated Vascular Ageing After COVID-19 Infection: The CARTESIAN Study

While we've seen estimates of up to 1 in 5 adults experiencing some form of PASC, other studies have shown a much lower incidence; sometimes in the single digits. We've also seen studies that suggest - since the arrival of Omicron in late 2021 - the incidence and/or severity of `Long COVID' has dropped.

But nearly all of these reports rely heavily on the medical coding systems, which adopted a `Post-COVID syndrome' ICD-10 code (U09.9) in late 2021, but which is only used at the discretion of the treating physician.

Some clinicians may avoid coding for PASC because it is largely a diagnosis of exclusion, and they may want to rule out other causes first. Others may consider it too broad, and prefer to code specific complaints like fatigue, dyspnea, or cognition problems.

As a result, when studies are based on EHR (Electronic Health Records) coding, they may miss many probable PASC cases.

In order to try to remove - or at least narrow - this blind spot, researchers created an AI tool that searched electronic health records for patterns of symptoms and diagnoses consistent with PASC, even though their chart may not have been coded as such.

There are limitations to this type of approach, as it relies heavily on the quality and quantity of the EHR documentation, and so it may have missed some PASC cases. At the same time, temporal association does not establish causation, and so these numbers should be taken with a grain of salt.

Still, it strongly suggests that the actual burden of PASC is considerably higher than the EHR coding reflects, and that the incidence of Long COVID was still increasing in 2024, two years after the shift to Omicron.

The full study is well worth reading in its entirety. I've posted the Abstract and summary below.

Original Investigation
Infectious Diseases
Long COVID Persistence and Surveillance Gaps Across 58 US Hospitals
Jiazi Tian, MSc1; Alaleh Azhir, MD, MSc1,2; Matthew Decaro, MSc3 et al

JAMA Netw Open
Published Online: May 27, 2026
2026;9;(5):e2614909. doi:10.1001/jamanetworkopen.2026.14909

Key Points

Question What is the true burden of chronic disease following COVID-19, and why does current surveillance fail to capture it?

Findings In this cohort study of 457 950 patients with COVID-19 across 58 hospitals, validated computable phenotyping identified postacute sequelae of SARS-CoV-2 infection in 16.28% of cases, 2-fold higher than diagnostic code–based surveillance. Of identified manifestations, 89.31% represented chronic conditions, with prevalence increasing through mid-2024.

Meaning These findings suggest that approximately 1 in 6 patients with COVID-19 develops postacute sequelae, predominantly chronic conditions currently invisible to surveillance systems, representing an accumulating rather than resolving health care burden.

Abstract

Importance Surveillance of postacute sequelae of SARS-CoV-2 infection (PASC) depends on diagnostic coding systems that capture fewer than one-half of affected individuals, rendering millions invisible to health systems and policymakers.

Objective To quantify the gap between true PASC burden and diagnostic code–based estimates, determine the proportion representing chronic disease, and characterize organ system heterogeneity and temporal trends across diverse populations.

Design, Setting, and Participants This retrospective cohort study used electronic health record data from 58 hospitals and affiliated clinics in 4 US regions, from 2017 to 2025. Adults (aged ≥18 years) with laboratory-confirmed SARS-CoV-2 infection or a COVID-19 diagnosis code were included. A custom artificial intelligence algorithm, the Precision Phenotyping for Research Cohorts (P2RC), was implemented using federated infrastructure.

Exposure Laboratory-confirmed SARS-CoV-2 infection or COVID-19 diagnosis code.

Main Outcomes and Measures The primary outcomes were PASC prevalence, the proportion classified as chronic conditions, organ system distribution, and temporal trends from 2020 to 2024. χ2 Tests were used to assess organ system heterogeneity across regions, and negative binomial regression was used to model quarterly temporal trends, yielding incidence rate ratios (IRRs) with 95% CIs.

Results In this cohort study of 457 950 COVID-19 cases (mean age, 52.05 years; 275 107 [60.07%] female), the P2RC algorithm identified 74 560 PASC cases (16.28% overall; 28 585 [18.58%] in New England, 978 [19.55%] in Southeast Texas, 10 534 [22.69%] in Southern California, and 34 463 [13.64%] in Western Pennsylvania), more than 2-fold higher than the proportion identified by code-based surveillance (<7%). Of 883 International Statistical Classification of Diseases, Tenth Revision, Clinical Modification codes associated with PASC, 594 (67.27%) represented chronic or potentially chronic conditions. Of 74 560 patients with PASC, 66 587 (89.31%) developed chronic conditions requiring ongoing clinical management; this represents 14.54% of the total number of 457 950 patients with COVID-19. Substantial organ system heterogeneity was observed (χ2 = 2504.73; P < .001): New England demonstrated thyroid-predominant endocrine patterns, while Southeast Texas, Southern California, and Western Pennsylvania showed metabolic-predominant profiles. Negative binomial regression revealed increasing PASC prevalence through mid-2024 (IRR per quarter, 1.01 [95% CI, 1.00-1.01; P < .001] in New England; 1.00 [95% CI, 1.00-1.01; P < .001] in Southern California; and 1.02 [95% CI, 1.01-1.02; P < .001] in Western Pennsylvania), indicating an accumulating rather than resolving burden.

Conclusions and Relevance In this cohort study, approximately 1 in 6 patients with COVID-19 developed PASC, and 89.31% of these patients had at least 1 chronic condition. Current diagnostic coding captured fewer than one-half of the cases, obscuring a substantial chronic disease burden. The persistently increasing prevalence through 2024 indicated an accumulating health care burden requiring investment in surveillance infrastructure and integrated care pathways.

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ECDC Ebola Update & Individual Country Responses From Canada, U.S. & Taiwan

2026-05-27T08:40:17.059-04:00

Full PPE – Credit Emory University

#19,179

Despite what the tabloids and the clickbait internet machine might try to imply, the risk of Ebola Bundibugyo sparking a pandemic is incredibly low. Barring some extraordinary evolutionary leap, Ebola viruses are simply not transmissible enough to pose a global threat.

But, as was well demonstrated a dozen years ago in West Africa (see below), Ebola is quite capable of sparking a horrendous, and prolonged, regional epidemic.

The CDC's brief synopsis of the 2014-2016 West Africa outbreak describes 28,610 cases and 11,308 deaths; although the true number was likely higher. During this outbreak, dozens of cases were exported to other regions (see list below), including to Italy, Spain, the UK and the United States.

Credit Managing emerging transnational public health security threats: lessons learned from the 2014 West African Ebola outbreak

The in-hospital cost of treating a single Ebola patient can run 500K-1M, and the costs of contact tracing, testing, and quarantining hundreds of potential contacts can run into the tens-to-hundreds of millions.

There are other costs, of course. Including canceled travel, reduced public activities, and surges in ERs due to the `worried well'. Even a small-to-moderate cluster of cases in the United States, Europe, or Canada could easily carry a billion-dollar price tag.

So it is little wonder that countries are concerned. And as the ECDC stated this morning, in many ways the Bundibugyo virus outbreak in the DRC and Uganda is unlike any previous ebola outbreak.

ECDC increases activities as Ebola outbreak in DRC and Uganda intensifies

Press release
27 May 2026

As the Ebola disease outbreak in the Democratic Republic of the Congo (DRC) and Uganda develops rapidly, the European Centre for Disease Prevention and Control (ECDC) is ratcheting up its support on the ground, while continuing to emphasise that the risk of infection to the general population in Europe remains very low.

The current outbreak is of serious concern, and is in many ways not comparable with previous Ebola outbreaks. The highly complex situation in the affected region makes it considerably more difficult to take effective countermeasures. The circumstances are made still more challenging by the fact that this outbreak is caused by Bundibugyo virus, for which there is currently no licensed vaccine or specific treatment.

In order to gather first-hand information from the field, ECDC is working closely with partners to establish a larger presence via the EU Health Task Force to support DRC and Uganda. This will also enable the Centre to gather more detailed information on exit screening, which ECDC continues to emphasise is crucial to reduce risk by identifying travellers who are symptomatic. It will also allow ECDC to promptly update its risk assessment and recommendations for the European Union and European Economic Area (EU/EEA).

The action ECDC is taking to support health authorities in the affected countries while ensuring the health security of people in the EU/EEA includes:

Support to EU/EEA countries to provide clear and practical travel advice for all those arriving from the affected areas, including what to do if they develop symptoms
Assistance to EU/EEA countries in strengthening readiness to rapidly detect and isolate anyone infected who is arriving from the regions affected and carry out all necessary control measures
Daily epidemiological updates
Forthcoming ECDC scientific advice on infection prevention and control measures in the EU/EEA
Deployment of an ECDC expert to the Africa Centres for Disease Control and Prevention as part of the EU Health Task Force to support coordination and operational planning
As a further step, a larger deployment of ECDC experts to the region via the Task Force is in progress
Work on a modelling study on the likelihood of importation of cases into the EU/EEA
Cooperation with the aviation sector to strengthen the safety of all passengers on board, ensuring a consistent approach to the management of suspected cases during flights
Development of a series of infographics for policymakers, healthcare practitioners, and the general public
More than 900 suspected cases of Ebola disease were reported in DRC as of 24 May 2026. Uganda has so far reported seven cases. ECDC continues to assess the likelihood of infection for anyone from the EU/EEA living in or travelling to affected areas as low, provided they follow the recommended precautionary measures.

While there are long-standing general agreements not to restrict travel and trade during disease outbreaks like this in the 2005 IHR agreement, since COVID, countries have been increasingly willing to go their own way.

Five days ago we looked at the U.S. Enhanced Ebola Airport Screening protocols, which allows non-symptomatic U.S. passport holders with travel history to the affected region to proceed on to their final destinations (with appropriate healthcare advice).

Late yesterday, Canada announced their own - far more restrictive - policy, which will require a 21-day quarantine period upon arrival from the DRC, Uganda, or South Sudan.

Government of Canada introduces temporary border measures in response to the Ebola disease outbreak

From: Public Health Agency of Canada

News release

May 26, 2026 | Ottawa, Ontario | Public Health Agency of Canada

In response to the Ebola disease outbreak in the Democratic Republic of the Congo, and increasing risks in Uganda and South Sudan, the Government of Canada is taking decisive action by introducing temporary border measures to reduce the risk of the virus entering and spreading within Canada.

The Government of Canada intends to suspend immigration documents for residents of countries that have a high or very high risk of outbreak of Ebola disease for the next 90 days beginning May 27, 23:59 EDT. At this time, this includes the Democratic Republic of the Congo, Uganda and South Sudan. This will mean that even those with a previously approved temporary resident visa, electronic travel authorization (eTA) or permanent resident visa will not be allowed to travel to Canada while their immigration document is suspended. During this time, we also intend to temporarily pause making decisions on applications for these documents from residents of these countries.

The government intends to implement an additional measure effective May 30 at 23:59 pm EDT until August 29, 2026, whereby Canadian citizens, permanent residents, persons registered under the Indian Act, and foreign nationals, who have been in these areas within the previous 21 days and do not have symptoms, will have to quarantine for 21 days. If they do not have a place where they can quarantine safely, they will be provided with an appropriate location. Travellers who have symptoms will be isolated at a hospital for further assessment. These measures are being implemented under the Quarantine Act.

Those who are already in Canada are not impacted by these measures, and may continue to stay here for their authorized period of stay. As per standard procedure, these travellers were already screened upon their arrival by a Canada Border Services Agency Border Services Officers. Canadian citizens and permanent residents could still return to Canada and would undergo screening at ports of entry upon their arrival.

While the risk to people in Canada remains low, the Government of Canada is taking a precautionary approach given the severity of Ebola disease and the evolving international situation, including the FIFA World Cup 2026 ™. There has never been a case of Ebola disease imported into Canada and there are currently no cases of Ebola disease in North America.

The Government of Canada continues to monitor the situation closely and will adjust these measures as needed based on available evidence, including the epidemiological situation in Canada and internationally.

Travellers are reminded that border measures may change with little notice and are encouraged to check the latest information before travelling at travel.gc.ca.

As we discussed last January in Hazard Identification and Risk Assessment (HIRA) For the FIFA World Cup 2026, this summer Toronto, Canada will host 6 FIFA World Cup matches in June and early July, with at least 300,000 visitors expected to descend on the city.

In total, 16 cities across 3 countries (Canada, Mexico, U.S) will host the 2026 world cup, with over 5 million fans expected to travel to the various venues.

Even a whiff of an Ebola scare this summer could be devastating to their economies; a factor which likely loomed large in Canada's calculations.

Nestled somewhere between Canada's more restrictive `containment' model and the U.S.'s `monitor and manage' strategy, Taiwan's CDC announced a mandatory 21-day `self-health management' policy for arrival from the affected region.

(Translation)

In response to the rapid development of the Ebola international outbreak, the Centers for Disease Control (CDC) has raised the travel advisory level for the Democratic Republic of Congo and Uganda to Level 3, "Warning," and strengthened cross-border prevention measures. Travelers with the aforementioned travel history must undergo 21 days of self-health management.

Release Date: 2026-05-27

The Centers for Disease Control (CDC) announced today (May 27) that the Ebola outbreak in the Democratic Republic of Congo (DRC) and Uganda, which the World Health Organization (WHO) declared a Public Health Emergency of International Concern (PHEIC) on May 17, 2026, has recently developed rapidly and is becoming increasingly severe. In addition to Ituri Province in the DRC being an outbreak hotspot, cases have also been reported in North Kivu and South Kivu provinces of DRC, as well as neighboring Uganda, indicating a spreading trend. As of May 24, the DRC had a cumulative total of 112 confirmed cases (including 11 deaths) and 906 suspected cases (including 223 suspected deaths), with one US citizen diagnosed after contact with the virus at a local medical facility. Furthermore, Uganda has also reported 7 confirmed cases (including 1 death), all highly related to the DRC outbreak.

The Taiwan Centers for Disease Control (CDC) announced that, to reduce the risk of imported Ebola cases, Taiwan is strengthening cross-agency security measures at its borders and enhancing port monitoring and interception mechanisms, effective immediately. For travelers arriving from the Democratic Republic of Congo and Uganda, quarantine personnel will conduct enhanced TOCC (Travel, Occupation, Contact, and Cluster History) and health assessments.

All travelers must undergo 21 days of self-health management upon arrival. Those assessed as potentially at risk of Ebola infection will be immediately transported by ambulance to contracted hospitals for examination, with simultaneous coordination with local health authorities for prevention and control efforts.

The CDC explained that the Ebola outbreak is currently experiencing a rapid surge, and the actual fatality rate is likely far higher than currently reported official figures. This outbreak is occurring in a complex environment intertwined with security threats and humanitarian challenges. The lack of approved vaccines and specific treatments for this type of virus, coupled with local political instability and high population mobility, has significantly increased the difficulty of epidemic prevention. The WHO assesses that the actual scale of infections is likely far greater than the currently reported numbers, and has rated the risk level of the Democratic Republic of Congo as "very high," Uganda and surrounding areas as "high," and the global risk as "low."

(Continue . . . )

While this translation uses polite wordage like `requested to', and `cooperate with', there is a bit of a sting in the tail of this announcement.

Asymptomatic passengers will be issued a "Notice of Self-Health Management for Passengers with Travel History to Ebola-Epidemic Areas." Upon arrival, passengers are requested to cooperate with 21 days of self-health management, keep their phones accessible for contact tracing by health authorities, take their temperature twice daily (morning and evening), and report their health status to the "Public Proactive E-Reporting System." If you experience any of the above symptoms, please immediately call the epidemic prevention hotline 1922 for assistance from the health bureau to seek medical attention. Failure to cooperate with these measures will be punished in accordance with the Communicable Disease Control Act.

The reality is, no one truly knows what the `right' measured response to this ebola outbreak is; they only know that the political, economic, and societal price of even a minor breach could be enormous.

So, as we saw during the opening days of COVID (see No Pandemic Plan Survives Contact With A Novel Virus), we are likely to see a wide variety of approaches.

Some may be overreactions, while others may be too complacent. But at least with this range of responses, we should come away with a better idea of what works - and what doesn't - which may prove useful for the next public health crisis.

Vaccines: Lessons from the 2024 avian influenza vaccination campaign in Finland: a qualitative inquiry

2026-05-26T08:05:25.643-04:00

#19,178

In 2023 Finland's fur industry was hit hard by HPAI H5N1, with more than 70 fur farms infected, and > 500,000 animals culled. After an uncertain start, the Finnish Food Agency ordered an aggressive quarantine and culling program, which was strongly opposed by the fur industry.

Following on the heels of a mink-variant COVID outbreak in 2020, these HPAI outbreaks also brought renewed calls for the banning of the fur trade in the EU, and around the globe.

Although outbreaks reports from fur farms declined by the end of 2023, this epizootic - combined with increasing avian flu activity around the globe - led the EU to order a significant quantity of H5 vaccine the following summer.

PRESS RELEASE 11 June 2024 Brussels
Commission secures access for Member States to 665,000 doses of zoonotic influenza vaccines to prevent avian flu

Today, the Commission's Health Emergency Preparedness and Response Authority (HERA) as part of its mandate on preparedness, has signed on behalf of participating Member States, a joint procurement framework contract for the supply of up to 665,000 pre-pandemic vaccine doses of the up-to-date Zoonotic Influenza Vaccine Seqirus, as well as an option for a further 40 million doses over the duration of the contract. Thanks to this contract the participating Member States will have access to medical countermeasures to prevent avian flu.

The vaccine is intended for those most exposed to potential transfers of avian influenza from birds or animals, such as poultry farm workers and veterinarians. It aims to prevent the spread or potential outbreaks of avian influenza in Europe, protecting citizens and livelihoods. The vaccine is the only preventive zoonotic avian influenza vaccine currently authorized in the EU.

(Continue . . . )

While the intent was to store these doses for use in a future outbreak, the EU carved out 20,000 doses for immediate use in Finland; specifically for the vaccination of high risk fur farmers (see Finland: MOH Announcement On Avian Flu Vaccine Availability For People At High Risk).

In August of 2024, Finland's THL Announced the Start Of H5 Vaccination For High Risk Groups. While details on the campaign were scant, last December, in a study published in Nature Microbiology, researchers discussed the disappointingly low uptake - particularly among fur farmers - of this vaccine.

The final sample size was smaller than planned due to recruitment challenges, largely reflecting the overall low vaccine uptake across all target groups. This was particularly evident among fur farm workers, none of whom participated despite repeated outreach efforts.

I've not been able to determine how many fur farmers actually accepted the vaccine, but it appears to be a small fraction of the roughly 860 people who received as least 1 dose.

All of which brings us to a new Short Communications, published in the journal Vaccines, which details the Finnish vaccination campaign and some of the perceived difficulties in convincing high-risk individuals to get the shot.

While the timing, logistics, and `divergent risk perceptions' were cited as barriers to vaccination, distrust of the government appears to have been the biggest factor.

They call it the `most unexpected barrier', but to anyone who has spent any time online - or actually talking to the public over the past 20 years - it can't have been that unexpected.

This report is based in large part on 17 interviews, of which only one was actually a farmer (poultry). Since no fur farmers were willing to talk to these researchers, many of their conclusions are - by necessity - based on 3rd-party assessments.

Despite these limitations, this is a fascinating look at the growing chasm between governmental expectations and the public's willingness to cooperate. I've only posted some excerpts, so follow the link to read it in its entirety.

I'll have a bit more after the break.

Short communication

Lessons from the 2024 avian influenza vaccination campaign in Finland: a qualitative inquiry

Vuokko Härmä a, Minttu Palsola a, Aapo Kuusipalo a b, Erika Lindh a, Merit Melin a, Hanna Nohynek a
https://doi.org/10.1016/j.vaccine.2026.128736
Under a Creative Commons license

Abstract

Highly pathogenicity avian influenza H5N1 (HPAI H5N1) viruses cause a continuous threat to wild avian populations. During recent years, spillover to both wild and domestic mammals has occurred with an increasing frequency. As a consequence of the recent developments in the epidemiological situation, the human-animal interface with the risk of human exposure to HPAI H5 has expanded.

In 2024, Finland became a global forerunner to offer H5 vaccine to occupational risk groups, specifically fur and poultry workers, following an extensive HPAI H5N1 outbreak in 2023 in fur-farmed minks and foxes. Despite targeted efforts to reach the people at increased risk, only 8,6% of the target population received the first dose and 7,5% completed both doses.

To seek a better understanding of the barriers behind low vaccine uptake a Behavioural and Cultural (BCI) insight approach was chosen. A rapid qualitative study was conducted in late 2024 (n = 17), utilising semi-structured interviews with health authorities, industry stakeholders, and risk group representatives in the Ostrobothnia region in Finland. Barriers were identified across three dimensions:

(1) logistical failures, including poor timing and difficulties in reaching target groups
(2) divergent risk perceptions, where economic livelihood overshadowed personal health risks; and
(3) political distrust, stemming from perceived stigmatization by national health authorities.

The results will provide vital information for future pre-pandemic communication and implementation strategies and helps to identify key stakeholders and target groups.

(SNIP)

3.3. Trust and political tensions
Perhaps the most unexpected barrier identified was the erosion of trust between the fur industry and national health authorities. Our analysis suggests that the campaign's reception was influenced by ongoing political and ethical debate regarding the future of fur farming in Finland.

The 2023 outbreak led to intense public debate and strict regulatory measures, including mass culling of animals in affected farms ordered by the Finnish Food Authority as part of outbreak control measures. Advocates of the fur industry publicly argued that such measures were excessive, and that the industry was being “scapegoated” for a natural phenomenon. Statements from national health and political figures during the outbreak were perceived by farmers as stigmatizing. Consequently, when these same national authorities recommended vaccination in 2024, the message was not welcomed but was met with skepticism.

A dichotomy in trust was evident, while farmers generally maintained high trust in local occupational healthcare nurses and municipal doctors, they expressed deep distrust toward national authorities. National-level communication was characterised as bureaucratic, distant, and sometimes “accusatory”. Participants reported that official messaging was perceived as stigmatizing for the fur farmers for the zoonotic risk, which reduced willingness to comply with voluntary measures.

Additionally, local media in the region were reportedly hesitant to publish pro-vaccination content related to avian influenza, fearing backlash from a community already feeling under siege. This created a vacuum of positive reinforcement, further limiting the reach of health messaging.

(SNIP)

4. Conclusion and implications

The low uptake of the H5 vaccine in Finland serves as a critical case study in the challenges of implementing public health interventions within agricultural and occupational settings that have been involved in political tensions. Achieving high vaccination coverage can be particularly challenging when the target population experiences a combination of marginalisation and structural distrust. However coverage was low across all target groups, which further indicates structural and communicational challenges.

(SNIP)

While the socio-political climate of the Finnish fur industry is unique and findings should be applied cautiously to other contexts, this study offers broader insights for One Health interventions. They demonstrate that preparedness requires more than just clinical readiness; it demands a multisectoral strategy that aligns public health goals with the economic and social realities of the agricultural sector. Vaccination outcomes are shaped by context-specific social, political, and cultural factors, which must be considered to ensure optimal uptake.

(Continue . . . )

While the embattled fur farming community is probably not the best proxy for attitudes of the rest of the world's population, convincing the public to take any experimental vaccine in the absence of an imminent high-morbidity/mortality outbreak is always going to be a tough sell.

Today, trust (and uptake) in vaccines has plummeted, while warnings from the WHO, or the CDC, are often dismissed as hyperbole or part of some conspiratorial `plandemic'.

Although most of this is ginned up out of whole cloth by clickbait videos and deranged social media posts, some of this mistrust has been rightfully earned (see When Scientists Behave Badly).

When the next global public health threat begins its world tour, governments and health agencies are going to be desperate to find some way to regain the trust - and cooperation - of the public.

And right now, that's not a battle they appear to be even close to winning.

Upcoming COCA Call: What Clinicians Should Know about Ebola Bundibugyo Virus

2026-05-26T04:59:14.523-04:00

#19,177

Later this week (Thursday, May 28th) the CDC will hold a COCA Call for clinicians and other healthcare professionals on the Ebola Bundibugyo Virus, which is spreading with alarming speed in the DRC and Uganda.

While the CDC has instituted airport screening - the potential still exists for imported cases to arrive in the United States - much as it did in the fall of 2014 during the West African outbreak (see NEJM: Ebola in the United States — Public Reactions and Implications).

In an effort to better prepared clinicians for potential cases, the CDC will hold a (roughly) 1-hour webinar this week on this emerging virus. These presentations are often technical, and are of greatest interest to clinicians and healthcare providers, but are also archived within a few days, and made available to the general public.

Details are limited, but I've reproduced the announcement below.

What Clinicians Should Know about Ebola Bundibugyo Virus

For Health Care Providers
May 28, 2026

At a glance

During this COCA Call, learn more about this outbreak, the history and ecology of Bundibugyo virus, what U.S. clinicians should know about preparing for, diagnosing, and managing patients with suspect or confirmed Ebola disease, and how to prevent Ebola viruses from spreading.

Overview

The Centers for Disease Control and Prevention is responding to an outbreak of Ebola Bundibugyo virus disease in the Democratic Republic of the Congo and Uganda. The overall risk to the American public and travelers remains low, but as with other high-consequence infectious diseases, clinicians are often the first to diagnose an outbreak. During this COCA Call, learn more about this outbreak, the history and ecology of Bundibugyo virus, what U.S. clinicians should know about preparing for, diagnosing, and managing patients with suspect or confirmed Ebola disease, and how to prevent Ebola viruses from spreading.

Webinar

Thursday, May 28, 2026

2:00 – 3:00 PM ET

A few minutes before the webinar begins, please click this link to join.

COCA Call Objectives

After completing this course, the learner will be able to:
Cite background information on the topic covered during the presentation.
Identify CDC's role in the topic covered during the presentation.
Describe the topic's implications for clinicians.
Identify concerns and issues related to preparedness for and response to urgent public health threats.
Identify how an interprofessional team of healthcare providers can work with patients to promote disease prevention.

Continuing Education

Continuing education is not offered for this COCA Call.

Target Audience

Physicians
Nurses
Pharmacists
Veterinarians
Physician Assistants
Health Educators
Other Clinicians
Additional Information Contact Information: coca@cdc.gov
Support/Funding: Centers for Disease Control and Prevention, Office of Emergency Risk Communication

Method of Participation: You may participate in the educational activity by viewing the program information above.

Virulence: Surveillance and biological characterization of H3 subtype avian influenza viruses in Eastern China

2026-05-25T08:09:27.855-04:00

Credit ECDC

#19,176

Over the past few years we've seen a noticeable uptick in interest by Chinese researchers into H3 virus evolution, particularly in Eastern China's poultry. While perhaps not as alarming as H5N1, H3 viruses have a long history of spilling over into humans and causing pandemics (see graphic above).

The avian H3N2 pandemic virus emerged in 1968, and while it killed somewhere between 1-4 million people during the pandemic, it has killed many times more than that over the past 56+ years.

A little over 20 years ago (2004) an equine H3N8 virus jumped to dogs in Florida, before spreading globally. Three years later, an avian H3N2 virus in South Korea, followed suit, with both reassorting with other subtypes (see J. Virology: Zoonotic Risk, Pathogenesis, and Transmission of Canine H3N2).

In 2011 avian H3N8 was found in marine mammals (harbor seals), and 2012’s mBio: A Mammalian Adapted H3N8 In Seals, provided evidence that this virus had recently adapted to bind to alpha 2,6 receptor cells, the type found in the human upper respiratory tract.

In 2015's J.Virol.: Experimental Infectivity Of H3N8 In Swine, we saw a study that found that avian (but not canine or equine) H3N8 could easily infect pigs.

All worrisome signals, but it was the 2022 emergence of a zoonotic H3N8 virus in China - first infecting 2 children 400 km apart in Henan and Hunan Provinces in April and May of 2022 - and more recently a fatal infection of a 56 year old woman in Guangdong Province, that really raised concerns.

This led to 2023's EID Journal: Evolution of Avian Influenza Virus (H3) with Spillover into Humans, China, where researchers described finding 4 sub-lineages and an astonishing 126 genotypes of avian H3 viruses circulating in China.

The authors also described a recent reassortment event where H3N8 acquired the internal genes from LPAI H9N2, a promiscuous virus which had previously contributed genes to both H5N1 and H7N9 (see PNAS: Evolution Of H9N2 And It’s Effect On The Genesis Of H7N9).

Since then, we've looked at a number of cautionary reports on H3 viruses from China, including:

J. of Infection: Global Spread of H3 Subtype Avian Influenza Viruses With an Accelerated Evolution After Interspecies Transmission

Vet. Research: Emergence of a Novel Reassortant H3N3 Avian Influenza Virus with Enhanced Pathogenicity and Transmissibility in Chickens in China

Transboundary & Emerg. Dis.: H3 Avian Influenza Virus Isolated from China in 2021–2022 Showed the Emerging H3N8 Posed a Threat to Human Health

Eurosurveillance: Analysis of Avian Influenza A (H3N8) Viruses in Poultry and their Zoonotic Potential

To this list we can add the following report, published last week, in the journal Virulence.

Viral Pathogenesis
Surveillance and biological characterization of H3 subtype avian influenza viruses in Eastern China

Xinyu Miao , Xinyi Zhao , Nan Zhang , Yinyan Yin , Xing Xu , Jinyuan Wang ,
Article: 2673657 | Received 04 Nov 2025, Accepted 09 May 2026, Published online: 19 May 2026 https://doi.org/10.1080/21505594.2026.2673657

ABSTRACT

H3 subtype avian influenza viruses (AIVs) are frequently detected in poultry and wild birds, however, systematic characterization of contemporary isolates remains limited. We aimed to investigate the genetic evolution, pathogenicity, and transmission characteristics of H3 subtype AIVs circulating in Eastern China.

Seven H3 subtype AIVs isolated between 2014 and 2021, including five H3N2, one H3N3, and one H3N6 strain, were analyzed. Phylogenetic analysis showed that all isolates belonged to the Eurasian lineage. Evidence of extensive reassortment with other AIV subtypes, as well as adaptive mutations associated with pathogenicity, and cross-species transmission, particularly in H3N2 subtype AIVs, was identified.

Notably, H3N2 subtype AIVs exhibited dual receptor-binding properties, recognizing both SA α-2,3-Gal and SA α-2,6-Gal receptors. Although all isolates demonstrated low pathogenicity in chickens, mice, and guinea pigs, variations in transmission efficiency were observed.

The H3N2 strain A/Duck/Anhui/LY/2021 showed the highest capacity for cross-species and aerosol transmission among guinea pigs. Overall, these findings indicate that H3 subtype AIVs have the potential for cross-species transmission and highlight the importance of continued surveillance of H3 subtype AIVs circulating in nature.

(SNIP)

Discussion

In April 2022, the first human infection with the H3N8 virus was reported in Henan Province, China [Citation50]. In May 2022, a second case was identified in a 5-year-old boy in Hunan Province, China [Citation16]. These events have raised substantial concerns regarding the potential public health impact of emerging H3N8 subtype AIVs. In addition to H3N8 subtype AIVs, H3N2 subtype AIVs are continuously detected in poultry throughout the year in southern China, according to epidemiological surveys [Citation51].

Previous studies have demonstrated that H3N2 subtype AIVs can be transmitted between guinea pigs and ferrets via respiratory droplets [Citation2]. Furthermore, recent isolates have acquired mutations associated with increased binding affinity for human-type receptors and enhanced transmissibility in ferrets, posing a potential risk to human health [Citation52].

In China, H3N2 subtype AIVs are widely detected in LPMs [Citation44], increasing the likelihood of cross-species transmission from avians to mammals. Therefore, the cross-species transmission potential of H3N2 subtype AIVs, particularly from avians to mammals, warrants close attention. Phylogenetic analysis in this study showed that all seven H3 subtype AIVs belong to the Eurasian lineage, within which multiple cross-species transmission events have historically occurred. Notably, H3N2 subtype AIVs (LY strain), presented potential cross-species transmission characteristics from avians to mammals, which should be more attention.

(SNIP)

In conclusion, H3N2 subtype AIV, particularly the LY strain exhibited both interspecies and cross-species transmission characteristics, suggesting an increased potential for transmission from avian to mammalian hosts.

These findings imply that continued surveillance of H3N2 AIVs in LPMs is critical, as they may pose an emerging concern to public health, and monitoring key molecular markers associated with mammalian adaptation could help in predicting and preventing future cross-species transmission events [Citation 59].

(Continue . . . )

Although the authors present no evidence of an immediate threat, H3 viruses have a proven pandemic track record, and we continue to see signs of a shift towards dual receptor-binding properties (avian & mamamallian) which should be viewed as concerning.

While there are many routes to the next pandemic (and not all of them involve novel influenza), twice in my lifetime an avian flu virus has emerged as a pandemic strain (H2N2 in 1957 and H3N2 in 1968).

A third flu pandemic (H1N1) emerged from swine in 2009, and currently 4 of the top 10 emerging zoonotic threats on the CDC's IRAT list are swine-variant viruses, with China's Avian-like H1N1 swine flu virus at the top of the list.

And as we've discussed often over the past few years (see Are Influenza Pandemic Viruses Members Of An Exclusive Club?), the progression of human influenza pandemics over the past 130 years has been H2, H3, H1, H2, H3, H1, H1.

Which suggests that - while an H5, H7, H9, or even H10 pandemic is always possible - the odds probably favor seeing an an avian, swine, or canine emerging H1, H2, or H3 virus as our next pandemic threat.

Which is why we follow research papers like today's with particular interest.

Nature Comms: Dairy cows infected with influenza A(H5N1) reveals low infectious dose and transmission barriers

2026-05-24T08:54:50.620-04:00

Credit EID Journal

#19,175

Nearly a year ago (June 2025) we looked at a Preprint: Dairy Cows Infected with Influenza A(H5N1) Reveals Low Infectious Dose and Transmission Barriers that suggested that the popular belief about how HPAI H5 was transmitting between dairy cows was either flawed, or at least incomplete.

The initial assumption by the USDA had been that the B3.13 genotype entered dairy cattle via a single spillover from birds - in the spring of 2024 in Texas - and was then spread to other states by the interstate transport of infected cattle.

This spillover was treated more-or-less as a fluke, since cattle were not considered particularly susceptible to influenza infection. The B3.13 genotype was somehow unique, and the threat of seeing additional spillovers was deemed low.

Cow-to-cow transmission within these herds was quickly hypothesized to be due to contaminated milking machines, although other routes of infection could not be ruled out (see EID Journal: Persistence of Influenza H5N1 and H1N1 Viruses in Unpasteurized Milk on Milking Unit Surfaces).

But cracks in these assumptions were starting to appear.

In May of 2024, we learned that the USDA had detected H5N1 In Alpacas (B3.13), which had apparently spilled over from poultry.
By July, Germany's FLI demonstrated that European H5 genotypes could also infect cattle
In August we saw a Preprint: Highly Pathogenic Avian Influenza H5 Virus Exposure in Goats and Sheep (in Pakistan)
In early 2025, the `single spillover' theory took another hit when a 2nd, and then a 3rd, spillover of a new (D1.1) genotype occurred in Nevada and Arizona.
And in March of 2025, we saw a study (see Virology: Detection of Antibodies Against Influenza A Viruses in Cattle) which reported that bulls and steers were just as likely to carry antibodies to (non-HPAI H5) IAV as cows and heifers

By last summer - despite limited cooperation from many farmers, and an almost exclusive focus on testing lactating dairy cows - the USDA had confirmed 1,073 infected herds across 17 states.

Last summer's preprint raised additional concerns, because they were unable to duplicate the suspected transmission of HPAI by contaminated milking machines under laboratory conditions.

They wrote:

In this study, we demonstrate that a low dose of virus is sufficient to establish robust intramammary infection, which may underlie the widespread and efficient transmission of influenza A(H5N1) in dairy herds.

However, sentinel cows repeatedly exposed to contaminated milking equipment and cohoused with infected cows did not become infected, indicating that cow-to-cow transmission observed on dairy farms may depend on factors that are not easily replicated under experimental conditions in high biocontainment research settings.

Since then we've seen the size and scope of HPAI H5 in cattle, ruminants, and other mammals continue to expand, with reports from both North America and Europe.

UK Defra: H5N1 Detected In Domestic Sheep with Mastitis

Norway Veterinary Institute: First discovery of H5N1 in sheep in Norway

Netherlands: NOS.NL Reports 5 Dairy Cows Have Now Tested Positive for H5N1

Transboundary & Emerg Inf: Serological Evidence of HPAI (H5N1) in Invasive Wild Pigs in Western Canada,

EID Journal: Highly Pathogenic Avian Influenza A(H5N1) Virus RNA in Bovine Semen, California, USA, 2024

While the number of new herds reported infected in the United States has dropped dramatically, testing remains both narrow in scope and limited, and the full extent of HPAI's spread is likely unknown.

All of which brings us to an update to last year's preprint, now in press for Nature Communications, which finds (a year later) that many questions regarding the transmission of HPAI in dairy cattle remain unanswered.

The full report is very much worth reading. I've only posted some highlights below, so follow the link. I'll have a bit more after the break.

Dairy cows infected with influenza A(H5N1) reveals low infectious dose and transmission barriers

Carolyn Lee, Natalie N. Tarbuck, Hannah J. Cochran, Bryant M. Foreman, Patricia Boley, Saroj Khatiwada, Alok Dhakal, Khadijat O. Adefaye, Jennifer Schrock, Mohammad Jawad Jahid, Thamonpan Laocharoensuk, Raksha Suresh, Olaitan Shekoni, Erika Stevens, Sara Dolatyabi, Christina Sanders, Elizabeth Ohl, Devra Huey, Juliette Hanson, Kara Corps, Renukaradhya Gourapura, Richard J. Webby, Cody J. Warren, Scott P. Kenney & Andrew S. Bowman

Nature Communications (2026) Cite this article

PDF

ABSTRACT

Highly pathogenic avian influenza A(H5N1) virus exhibits a strong tropism for the bovine mammary gland, challenging our understanding of influenza A virus host range and tissue specificity.

We performed experimental studies with an influenza A(H5N1) B3.13 genotype virus in female lactating dairy cattle to define the infectious dose, routes of exposure, and factors linked to morbidity and mortality. Here, we demonstrate that intramammary inoculation with as few as 10 TCID50 establishes a robust infection and shedding of high -titer virus in milk .

Despite this low infectious dose, H5N1 does not readily transmit via contaminated milking equipment and close contact with infected animals. High - dose intramammary exposure results in severe disease and mortality, while respiratory and oral exposure s are less likely to establish productive infection and associated morbidity.

This study challenges current hypotheses of H5N1 transmission on dairy farms, raising important questions about potential agent, host, or environmental cofactors contributing to viral spread .

(SNIP)

While the mammary gland appears to be a primary site of viral replication in dairy cows, the initial route of transmission from wild birds remains unclear. This uncertainty, along with the potential for respiratory exposure in milking parlors19,28, prompted our investigation of intranasal inoculation as a possible route of infection.

The macroscopic lesions observed in the respiratory tract suggest that influenza A(H5N1) B3.13 genotype can cause subclinical pathology in bovine respiratory tissues. However, the absence of clinical disease ( e.g. , fever, decreased milk production , and feed intake) , or virus present in milk at any time point indicates that this route of infection likely does not contribute to systemic disease and introduction into mammary tissue.

Additionally, chickens co -housed in open air cages adjacent to intranasally inoculated cows did not become infected as evidenced by lack of viral nucleic acid in swabs and overt disease despite salivary contact between an inoculated cow and chicken feed. We attribute this lack of transmission to multiple factors including limited viral shedding from nasal secretions and potentially high number of air changes (i.e., BSL - 3 engineering controls) in animal holding rooms.

Although human -to -human transmission of influenza A(H5N1) virus has not been reported, the persistence of the virus in dairy cattle and evidence of mammalian adaptation10, coupled with the broad and unprecedented host range, are alarming from a public health perspective.

A second, separate introduction of the D1.1 genotype virus, primarily circulating in wild birds, was reported in dairy cows in early 2025. Unlike the B3.13 virus circulating in cattle, this D1.1 genotype has been associated with severe disease in humans, resulting in two deaths 31 –33 —a highly concerning feature should this genotype continue to spread unfettered.

Further, the co -circulation of B3.13 and D1.1 viruses in dairy cows increases the risk of reassortment and viral evolution and complicates efforts to control the influenza A(H5N1) outbreak. Additional studies are needed to characterize the immune response and assess the level of protection following re -exposure to both homologous and heterologous influenza A(H5N1 ) viruses.

The mechanism of transmission within and between dairy herds is a critical question that remains and urgently needs to be answered.

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While I would love to be able to point to a single individual, agency, or special interest group that I believe to be the bottleneck for this investigation, the reality is this is a complex, highly unusual outbreak, dispersed over > 1000 locations across the nation.

Cattle are often asymptomatic, and infections tend to be transient, making the testing of individual cows impractical. Lactating cattle are more easily tested (via bulk milk sampling), and so that's where the virus has mostly been identified.

We're HPAI H5 in dairy cows perceived as being a much greater public health threat, I suspect we might be further along. But thus far, its impact on public health has been minimal. Of course, that could change.

Complicating matters, the answer to transmission on the farm is likely multifocal.

Despite the above findings, contaminated milking equipment may still play some part in HPAI transmission, as well as management of farm waste (manure), waste water runoffs, contaminated `milk disposal' practices, `aerosolization' in milking parlors, rodents and other peridomestic animals, and perhaps even flies or other insects.

PLos Bio: Surveillance on California dairy farms reveals multiple possible sources of H5N1 influenza virus transmission

We've been lucky in that HPAI H5N1 has yet to figure out how to transmit efficiently in humans, and at least in the United States, has been relatively mild in people. And it is even possible that cattle will prove to be a dead-end host for the virus.

But none of this is guaranteed.

If and when the next pandemic virus emerges the one thing we won't have in any abundance is time. Which makes anything we can do today to better understand the threats before us - and how to combat them - a wise investment for our future.

IORV: Inflammation and Cardiac Dysfunction in Hospitalized Patients With Influenza: The FluHeart Study

2026-05-23T07:22:50.387-04:00

#19,174

Over the past 15 years we've seen growing evidence that influenza (and other respiratory) infections can raise the risk of heart attacks and strokes, particularly in the acute phase of the illness, with elevated risks that may extend for weeks.

Eurosurveillance: Influenza Vaccination Attenuates Acute Myocardial Infarction and Stroke Risk Following Influenza Infection

JAHA: Viral Infections and Risk of Cardiovascular Disease: Systematic Review and Meta‐Analysis

Risk of Cardiovascular Events After Influenza: A Population-based Self Controlled Case Series Study

While the exact mechanism isn't fully understood, it appears that severe respiratory infections - which are often accompanied by hypoxemia, increased inflammation, hypotension, and hypercoagulability - can place enormous stresses on the cardiovascular system.

Adding to the growing evidence of an influenza-cardiovascular risk link, we have a prospective Danish study - published this week in Influenza & Other Respiratory Viruses - which found that > half of 241 hospitalized influenza patients showed evidence of cardiac dysfunction.

While this observational study cannot tell us whether influenza inflammation caused these cardiac dysfunctions, it suggests that increased inflammation and degraded cardiac function are often seen in conjunction with hospitalized patients with influenza.

A reminder that respiratory protection (vaccines, masks, good `flu hygiene',etc.) is also very likely heart protection. Follow the link to read the full report.

Inflammation and Cardiac Dysfunction in Hospitalized Patients With Influenza: The FluHeart Study

Kristoffer Grundtvig Skaarup, Filip Soeskov Davidovski, Emil Durukan, Ema Rastoder, Maria Dons, Morten Sengeløv, Bernadette Rasborg … See all authors
First published: 19 May 2026
https://doi.org/10.1111/irv.70266Digital Object Identifier (DOI)
PDF

ABSTRACT

Background

Influenza virus infection can lead to acute cardiovascular events, but the relationship between influenza-induced inflammation and cardiac dysfunction remains unclear. This study evaluated whether the severity of inflammation was associated with cardiac impairment, as assessed by echocardiography, in hospitalized patients with influenza.

Methods

In this prospective cohort study conducted in Denmark across three influenza seasons (2021–2022, 2022–2023, and 2023–2024), consecutive hospitalized patients with laboratory-confirmed influenza underwent protocolized echocardiography. Associations between C-reactive protein (CRP) levels and measures of cardiac function were assessed using multivariable models.

Results

Among 241 patients (median age, 73.2 years; IQR, 58.3–82.8; 53% female), 54% had left ventricular (LV) systolic dysfunction (ejection fraction < 50% or global longitudinal strain < 16%), 15% had signs of elevated LV filling pressure (E/e′ ≥ 14), 29% had right ventricular (RV) systolic dysfunction (tricuspid annular plane systolic excursion [TAPSE] < 1.7 cm or RV free wall strain < 20%), and 31% had pulmonary hypertension (RV systolic pressure [RVSP] > 40 mmHg). CRP showed a significant nonlinear association with E/e′, RVSP, and TAPSE. E/e′ and TAPSE worsened with higher CRP up to 100 mg/L, plateauing thereafter, whereas RVSP worsened at CRP levels > 100 mg/L.

Conclusions

Cardiac dysfunction was observed in more than half of all examined hospitalized patients with influenza. Higher levels of inflammation were independently associated with elevated LV filling pressure, pulmonary hypertension, and RV dysfunction, supporting a potential link between influenza infection and cardiac impairment.

(SNIP)

Discussion

In this prospective cohort study of hospitalized patients with laboratory-confirmed influenza infection, we made several key findings.

First, more than half of all patients exhibited LV or RV dysfunction.

Second, higher levels of influenza-related acute systemic inflammation, assessed by CRP, were associated with elevated LV filling pressure (E/e′), pulmonary hypertension (RVSP), and impaired RV systolic function (TAPSE).

These associations were independent of age, sex, preexisting cardiac and pulmonary conditions, and time since admission, supporting a potential inflammatory contribution to cardiac dysfunction during influenza infection.

This is the largest echocardiographic study of patients with influenza and the first prospectively conducted study to systematically evaluate cardiac function in patients hospitalized with laboratory-confirmed influenza. Furthermore, prior echocardiographic studies of influenza have not included speckle tracking technology, which enables more sensitive assessment of myocardial function [17]. The present findings extend previous evidence by suggesting that inflammation during acute influenza infection may contribute to cardiac impairment, beyond what would be expected from preexisting cardiac disease alone [18].

Additionally, the observed association between influenza-induced inflammation and cardiac dysfunction may help explain the seasonal increases in hospitalizations for new-onset and preexisting heart failure, as well as cardiovascular mortality, seen during influenza epidemics [4, 19].

(SNIP)

Conclusion

In this cohort of patients hospitalized with laboratory-confirmed influenza, more than half showed signs of either LV or RV dysfunction. Increased levels of influenza-induced inflammation were independently associated with elevated LV filling pressure, pulmonary hypertension, and RV dysfunction, indicating a possible direct connection between influenza infection and cardiac dysfunction.

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While I'm well past having to worry about dying tragically young - I'd still like to postpone the inevitable - so I get the flu shot every year, I've stayed current with my COVID vaccines, and have just added the Prevnar 20 pneumonia vaccine to my previous pneumovax protection.

Everyone has to make their own risk-reward calculation, of course. And none of these steps are guaranteed to be 100% effective.

But at my age, I'll take whatever advantage I can get.

ECDC Ebola Threat Assessment Brief

2026-05-22T10:14:30.042-04:00

#19,173

While it is still early days - and data remains sparse - the ECDC has produced a preliminary threat assessment for EU nations from the growing Ebola Bundibugyo outbreak in the DRC and Uganda.

Due to its length (n=9 pages), I've only reproduced the summary. Follow the link to read it in its entirety.

Ebola disease outbreak caused by Bundibugyo virus – Democratic Republic of the Congo and Uganda – 202621 May 2026

Summary
On 15 May 2026, Africa CDC reported an outbreak of Ebola disease in Ituri Province, DRC. Laboratory analysis at Institut National de Recherche Biomedicale of DRC identified Bundibugyo virus (BDBV). BDBV disease is a rare disease but can cause outbreaks with high case fatality rates. Considering the available information,complicated context and the uncertainties on the epidemiological information WHO declared a Public Health Emergency of International Concern on 17 May 2026. Africa CDC declared a Public Health Emergency of Continental Security on 18 May 2026.

This Threat Assessment Brief aims to assess the risk for people from the EU/EEA living in or travelling to affected areas and the overall risk of BDBV for the general population in the EU/EEA in the context of the ongoing outbreak of BDBV disease in DRC. It is intended for public health authorities in EU/EEA countries and is based on currently available evidence. It therefore carries considerable uncertainty.

Recommendations are also included for how public health authorities in the EU/EEA can strengthen preparedness and response capabilities.

Epidemiological situation

Based on data reported by the World Health Organisation as at 20 May 2026, almost 600 suspected cases and 139 deaths among the suspected cases have been reported. In DRC, 51 cases were confirmed in Ituri and North Kivu Provinces. While two imported cases were confirmed in Kampala, Uganda. At least five deaths had been reported among the confirmed cases as at 18 May, four in DRC and one in Uganda. Due to the very recentdeclaration of the outbreak and the uncertainties related to the epidemiological information, it is probable that theout break is larger than what is currently being reported, not only regarding the number of affected cases but also to its geographical extent. BDBV transmission requires direct contact with blood, or other bodily fluids of living or deceased infected people, or any surfaces and materials soiled by infectious fluids. Transmission can also occur through contact with dead or live infected animals, including handling and/or consuming bushmeat, or by visiting caves or mines colonised by bats. There are currently no licensed vaccines or specific treatments available for BDBV disease.

Risk assessment

Although epidemiological information remains limited and there are important uncertainties, the likelihood of infection for people from the EU/EEA living in or travelling to affected areas is assessed as low, provided they adhere to the recommended precautionary measures. Transmission requires direct contact with blood, secretions,organs, or other bodily fluids of dead or living infected people or animals; all unlikely exposures for the general EU/EEA travellers or expatriates in affected areas.

Staff members of humanitarian, religious and other organisations, particularly healthcare workers who are in direct contact with patients and/or local communities in the affected areas, are more likely to be exposed to the virus. Provided they adhere to the appropriate infection prevention and control measures, the likelihood of infection for this group is also low.
The most likely route by which the virus could be introduced to the EU/EEA is through people with a BDBV infection travelling from affected areas to the EU/EEA. During the Ebola disease outbreak in West Africa in 2013– 2016, which was the largest outbreak to date, where tens of thousands of cases were reported, with transmission in large urban centres, and hundreds of EU/EEA humanitarian and military personnel deployed to the affected areas, only a small number of imported cases to Europe were reported, most of them medically evacuated for treatment.

Based on this experience, it is expected that imported cases would be a rare event. The likelihood of secondary transmission of BDBV within the EU/EEA and the occurrence of sustained chains of transmission within the EU/EEA is considered very low, as cases are likely to be promptly identified and isolated and recommended control measures would be implemented. Although BDBV infection can cause severe disease in affected individuals, the population-level public health impact in the EU/EEA is expected to be very low because only very few cases would occur. Therefore, the overall current risk of BDBV for the general population in the EU/EEA is assessed to be very low.

Recommendations
EU/EEA countries should review and update the standard operating procedures on isolation and treatment for BDBV disease cases, and on contact tracing and quarantine for contacts of cases as needed.
EU/EEA public health authorities should:
1. Increase awareness among travellers to, and residents of affected areas, as well as returning travellers;
2. Increase awareness among health professionals on:

(i) the possibility of BDBV disease in travellers returning from affected areas;
(ii) the clinical presentation of the disease and the need to ask about the travel history and contacts of people returning from affected areas;
(iii) the availability of protocols for testing suspected cases;
(iv) infection prevention and control (IPC) procedures and appropriate management of suspected or confirmed cases.

3. Strengthen readiness to rapidly detect imported cases, promptly isolate them, and implement appropriate infection prevention and control measures.
4. Review testing capacity and BDBV diagnostic procedures. The EU reference laboratory for public health on Emerging, rodent-borne and zoonotic viral pathogens (EURL-PH-ERZV) offers diagnostic services to EU/EEA countries lacking capability to diagnose BDBV infection.
5. Minimise exposure in healthcare settings requires appropriate procedures, trained staff, and equipment for the safe management of BDBV cases.
6. Provide all returning travellers with clear information on symptoms, route of transmission, and what todo if symptoms develop after arrival in the EU/EEA: travellers who develop symptoms compatible with BDBV infection within 21 days after return should self-isolate, seek medical care promptly, and report their travel history and possible exposures.
Exit screening in affected countries, including symptom checks and exposure assessment, is crucial as it contributes to risk reduction by identifying symptomatic travellers before boarding and preventing travel while symptomatic. Exit screening also helps dissuade ill people from travelling and enhance public and stakeholder confidence. However, it cannot fully prevent exportation of cases, because absence of symptoms at departure does not exclude subsequent onset of disease.
ECDC actions
ECDC is monitoring the outbreak through its epidemic intelligence activities to provide epidemiological updates,situational awareness and assess the risk for the EU/EEA.

ECDC has deployed an expert through the EU Health Task Force to the Africa Centres for Disease Control and Prevention (Africa CDC) headquarters in Addis Ababa to support coordination and operational planning.

ECDC is in discussions with the European Civil Protection and Humanitarian Aid Operations (ECHO) and the Global Outbreak Alert and Response Network (GOARN) regarding the deployment of additional experts to support response activities in DRC and Uganda.

The European Union Reference Laboratory for public health on emerging, rodent-borne and zoonotic viral pathogens (EURL-PH-ERZV) offers support to the EU/EEA national reference laboratories for the diagnosis of BDBV infection, biosafety advice for handling and inactivation of samples, and also offers diagnostic services to EU/EEA countries for BDBV infection.

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Eurosurveillance: Cross-reactive human antibody responses to H9N2 influenza virus, New York, United States, 2025

2026-05-22T06:33:47.285-04:00

Credit NIAID

#19,172

While LPAI H9N2 remains far from our biggest pandemic concern, the CDC has designated 2 different lineages (A(H9N2) G1 and A(H9N2) Y280) as having at least some pandemic potential (see CDC IRAT SCORE), and several candidate vaccines have been developed.

Many will be surprised to find that, in terms of risk of emergence, the H9N2 Y280 lineage is ranked higher than H5N1, while the G1 lineage is ranked only slightly lower.

Although our concerns are primarily with the Asian lineages of H9N2, only a week ago in Preprint: Outbreak of H9N2 Avian Influenza Viruses in Lesser Rhea in Peru, June-July 2025 we looked at the unexpected emergence of a South American lineage.

H9N2 viruses are infamously promiscuous, and are constantly reassorting with other subtypes, which only increases their pandemic potential (see PNAS: Evolution Of H9N2 And It’s Effect On The Genesis Of H7N9).

All of which makes it important to know how much existing immunity their might be in the community should LPAI H9N2 ever embark on a world tour; particularly from regions of the world where the virus has not been circulating.

To that end we have the following Rapid Communication - published yesterday in the journal Eurosurveillance - which looks at a relatively small cohort (n=298) of serum samples collected in NYC between between Feb 2024 and Apr 2025, which they tested for signs of pre-existing immunity against 1 specific strain (A/Changsha/SR353/2025 - Y280 lineage) of LPAI H9N2.

In brief, they found widespread - but weak - cross-reactive haemagglutinin (HA)-binding antibodies among the 298 samples, likely due to previous seasonal flu vaccinations and/or exposures (see comparison chart below).

On the other hand, neuraminidase-inhibiting antibodies were more common and stronger. All this suggests that while protection against H9 infection is likely very limited - and unlikely to create much of a barrier for the spread of the virus - the stronger NA antibodies may help reduce the severity of infection.

At least that's the hope.

Interestingly, there is a small but perceptible dip in both HA and NA inhibition activity in those born in the mid-to-late 1980s and early 1990s, but given the small sample size and weak response, this may not be significant.

Although the news isn't all bad, this study looks at only one small and geographically limited dataset - and one specific strain of LPAI H9N2 - so there is only so much we can infer from their findings.

I've only posted the link and some excerpts below, most will want to follow the link to read the report in its entirety.

Open Access
Cross-reactive human antibody responses to H9N2 influenza virus, New York, United States, 2025
Gagandeep Singh1,2 , Disha Bhavsar1,2 , Lucas M Ferreri3 , Jessica R Nardulli1,2 , Charles Gleason1,2 , Neko Lyttle1,2 , Yuexing Chen1,2 , Anice C Lowen3 , Viviana Simon1,2,4,5,6 , Florian Krammer1,2,6,7,8

Avian influenza A(H9N2) viruses have been endemic in poultry for many years across Asia, the Middle East, and Northern and Western Africa and have been detected periodically in the Americas and Europe. Since their first detection in 1966, H9N2 viruses have evolved into multiple lineages and exhibit a high propensity for reassortment, contributing internal genes to zoonotic viruses such as H5N1, H7N9 and H10N8 [1,2].

Human infections with H9N2 viruses have been reported since 1998, with most cases linked to poultry exposure and typically resulting in mild or asymptomatic disease but severe cases and deaths have been observed as well. Despite these observations, population-level immunity to H9N2 remains poorly defined, particularly in regions without endemic exposure to the virus.

Here, we assessed cross-reactive antibody responses to H9N2 viruses using a panel of recently collected human sera from the general population of a large metropolitan city in North America (New York City)

(SNIP)

Our work describes pre-existing immunity at population level to avian influenza A(H9N2) viruses in adults from New York City. We observed widespread cross-reactive haemagglutinin (HA)-binding antibodies in the sampled group; however, these responses were of lower magnitude than those against seasonal H3. Consistent with this, HI and neutralising antibody responses to H9N2 were low or undetectable in most individuals, indicating limited functional immunity.

In contrast, a high proportion of individuals exhibited N2-binding and NI antibodies, including cross-reactive responses to H9N2. Although NA-directed antibodies do not prevent infection, they may reduce viral replication and disease severity, potentially providing the population with some degree of resilience against emerging influenza viruses [6,7]. The comparable magnitude of NI responses to H9N2 and H3N2 suggests that prior exposure to seasonal influenza viruses has generated cross-reactive NA immunity. This is consistent with historical observations that pre-existing anti-N2 antibodies, induced during circulation of A(H2N2) viruses, may have contributed to reduced disease severity during the emergence of the A(H3N2) pandemic [17,18].

The difference between HA and NA responses is not surprising. Comparative sequence analysis revealed substantial divergence between the HA proteins of lineage B4.7.2 virus A/Changsha/SR353/2025 (H9N2) and seasonal A/Thailand/8/2022 (H3N2), with only approximately 40% amino acid identity. In contrast, the N2 neuraminidases of the two viruses showed high conservation, sharing approximately 89% amino-acid identity.

Our study also has several limitations. Vaccination data were not captured, and we therefore cannot draw any conclusions about the effect of seasonal vaccination on H9N2 immunity. Furthermore, our analysis was restricted to a small, geographically limited group of individuals. Finally, different lineages of H9N2 circulate and they are antigenically distinct. This study only used one of these viruses as reagent and cross-reactive responses to other lineages of H9N2 may differ.

Conclusion

In summary, we found that pre-existing immunity to H9N2 in humans that is dominated by cross-reactive but largely non-neutralising antibodies, with a greater contribution from NA-directed responses. Given the pandemic potential of H9N2 viruses, these findings have important implications for risk assessment and support the inclusion of NA immunity in vaccine development strategies.

Further studies are needed to confirm whether cross-reactive NI antibodies confer protection against H9N2 infection or modulate disease severity, but our results suggest that the antibodies against H9N2 virus might derive from exposure to conserved epitopes shared between the avian-origin and seasonal strains.

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