Taiwan CDC: Human Infection with a Novel H7 Avian Virus

 

 #19,104

This morning we've an understandably lengthy, and detailed, (translated) report on Taiwan's first detection of a locally acquired human H7 LPAI infection in a poultry farmer.  

This is, according to this early account, due to a Eurasian H7 virus, and is not related to the H7N9 virus which swept China during the last decade (2013-2018). 

For now, it appears that only the HA (H7) has been identified, with additional tests pending. Throughout most of this press release the virus is referred to as a novel H7 and described as  `. . . a low-pathogenic avian influenza virus, without any mutations increasing the risk of avian-to-human transmission', although it is unclear how much of the genome has been characterized.

Note: in the google translation (below), at one point, the virus is referred to as H7N9, but a second translation (Bing) showed only H7. Pending further information, I suspect this was a translation glitch.

The patient (a man in his 70s) was hospitalized with fever and pneumonia on March 22nd, and remains hospitalized and in isolation, although his condition is said to be improving.  The CDC reports:

Currently, 33 close contacts are under health monitoring and management, and 3 have been given preventative medication based on risk assessment. Tests were conducted on 6 family members, all of whom tested negative.

While the patient raises poultry, none of his birds have tested positive for the H7 virus.  Movement of his birds has been halted, however, and agricultural authorities are now expanding their testing to nearby farms. 

The source of this man's infection remains under investigation.

First, the full press release, after which I'll have a bit more on past human H7 infections around the globe.

The first locally transmitted case of novel H7 influenza A has been detected in China. The agricultural and health departments have launched a joint prevention and control operation, collaborating on investigation and prevention.


Release Date: 2026-04-02

The Taiwan Centers for Disease Control (CDC) announced today (March 2nd) the first locally transmitted case of novel H7 subtype avian influenza in Taiwan. The patient is a man in his 70s from central Taiwan who works in poultry farming and has a history of chronic illness. He developed symptoms of runny nose, cough, and body aches on March 20th and sought medical attention at a hospital on March 22nd due to fever. He was admitted to the hospital on the same day.

Imaging examination revealed pneumonia. Based on clinical symptoms, test results, and the patient's contact history, the doctor reported the case as a novel H7 avian influenza and administered antiviral medication. Further testing and gene sequencing by the CDC confirmed the virus as H7 subtype avian influenza. Sequence analysis showed that this H7 belongs to the Eurasian lineage and is similar to the H7 subtype avian influenza viruses monitored in wild birds (mainly ducks and anadidae) in Taiwan over the years. 

However, it is different from the H7N9 subtype avian influenza virus that circulated in mainland China from 2013 to 2019, and is a low-pathogenic avian influenza virus. This morning, the CDC convened a meeting with agricultural authorities and relevant medical and veterinary experts to discuss the case and, based on the test results, confirmed it as a case of novel H7 avian influenza in humans. The patient's condition has improved and they are continuing isolation and treatment. 

The Centers for Disease Control (CDC) stated that after the first locally transmitted case of H7 subtype novel influenza A was detected in Taiwan, health and agricultural authorities immediately launched a joint epidemic prevention operation to carry out relevant investigations and prevention measures. Health authorities, with the assistance of epidemiologists and the Health Bureau, conducted on-site epidemiological investigations at the patient's residence, poultry farm, and hospital. Currently, 33 close contacts are under health monitoring and management, and 3 have been given preventative medication based on risk assessment. Tests were conducted on 6 family members, all of whom tested negative. 

Agricultural authorities immediately implemented movement restrictions at the poultry farm, and animal testing results were negative for avian influenza virus. To clarify the source of infection, today's expert meeting resolved to request the farm to expand testing at nearby poultry farms and to cooperate with wild bird associations to collect droppings from surrounding wild birds. Furthermore, the CDC will continue to cooperate with the farm to obtain the gene sequence of the H7 virus detected in Taiwan for further comparison. Health and agricultural authorities will continue to strengthen surveillance of humans and animals, including respiratory viruses and influenza/novel coronavirus pneumonia surveillance in medical institutions, active surveillance of poultry farms and migratory birds, and will cooperate with farmers to promote personal protective measures for poultry farmers and public health education. They have also contacted duck farming associations to distribute 40,000-50,000 masks free of charge to duck farmers. The

Centers for Disease Control (CDC) pointed out that, based on current epidemiological investigations and test results, the genetic analysis of this case shows a low-pathogenic avian influenza virus, without any mutations increasing the risk of avian-to-human transmission, and it remains a common avian virus. The initial assessment is that this case is an isolated incident.

Considering the patient's improved condition after treatment, the lack of mutations increasing the risk of avian-to-human transmission in the preliminary genetic analysis, the negative test results at the poultry farm, and the absence of any other family members showing symptoms after the patient's onset, the risk is assessed as controllable, and there is no immediate risk of the outbreak expanding.

 However, to understand the potential risks of this case, they will continue to track the symptoms and test results of contacts, further analyze the virus and trace possible sources of infection, and have activated a joint working group on the risk assessment of zoonotic infectious diseases between agriculture and health authorities to conduct a comprehensive risk assessment. The Taiwan Centers for Disease Control (CDC) will notify the World Health Organization (WHO) today through the IHR contact window in accordance with the International Health Regulations (IHR).

According to surveillance data, since the novel influenza A virus was classified as a Category 5 notifiable infectious disease in Taiwan in 2014, a total of 5 sporadic cases have been reported. Besides this case, the others were reported in 2017 (H7N9, imported from outside China), 2021 (H1N2v), 2022 (H1N2v), and 2023 (H1N2v). In addition, there were 4 confirmed cases of H7N9 imported from outside China in 2013-2014; none of the contacts were infected.

The CDC explained that the H7N9 sequence in today's reported case is only closely related to one other human case, H7N4, reported in Jiangsu, China in 2018. The case involves a 68-year-old woman with a history of coronary heart disease and hypertension. She developed symptoms such as cough, weakness, and muscle aches on December 25, 2017, and was hospitalized for pneumonia on January 1, 2018, and discharged on January 22 after recovery. Prior to the onset of illness, the patient had contact with live poultry. Her close contacts did not develop any suspected symptoms during the observation period. The virus remains avian and has not shown resistance to existing antiviral drugs.

The Centers for Disease Control (CDC) reminds workers involved in poultry and livestock farming to implement self-protection measures during operations and to conduct thorough disinfection after work to reduce the risk of infection with the novel influenza A. If symptoms of acute respiratory infection or conjunctivitis appear, seek medical attention immediately and proactively inform healthcare professionals of your occupational history of contact with animals to facilitate early diagnosis. The public is advised to implement the "5 Dos and 6 Don'ts" epidemic prevention principles in daily life:

"5 Dos": Cook meat and eggs thoroughly with soap; wash hands thoroughly with soap; if symptoms appear, wear a mask, seek medical attention immediately, and inform the doctor of your occupation and contact history; those who have long-term contact with poultry and livestock should get vaccinated against influenza; maintain a balanced diet and exercise appropriately.

"6 Don'ts": Don't eat raw poultry, eggs, or poultry products; don't smuggle or buy meat of unknown origin; don't touch or feed poultry and livestock; don't release or discard poultry and livestock indiscriminately; don't mix poultry and livestock with other poultry and livestock; and don't go to places with poor air circulation or crowded places.

For related information, please visit the Taiwan Centers for Disease Control website (https://www.cdc.gov.tw/) or call the toll-free epidemic prevention hotline 1922 (or 0800-001922).

Based on the available information, this spillover is being described as an `isolated incident', but as we've seen in the past, H7 viruses have shown some ability to spark larger outbreaks in humans. 

• In 2003, the Netherlands saw an outbreak of H7N7 that resulted in the loss of 30 million birds across 1,000 farms, and saw scores of mild human infections and the death of a veterinarian (see Eurosurveillance Human-to-human transmission of avian influenza A/H7N7, The Netherlands, 2003).

• Another analysis, performed by the RIVM (Ministry of Health) found the spread of the virus to be much greater than originally reported, citing as many as 1,000 human infections (see Executive summary Avian Flu Epidemic 2003: Public health consequences).

• Smaller H7 outbreaks, including the 2004 H7N3 outbreak in British Columbia, a small number of human infections in Wales in 2007, and 3 mild cases in Italy in 2013 (see ECDC : Human Infection By Avian H7N7 In Italy) were also reported.

• But the 5-year epidemic of H7N9 in China (2013-2018) - which hospitalized more than 1,500 people, killing roughly 40% of them - demonstrate just how formidable an H7 virus can be.

NYC's 2016 dramatic H7N2 outbreak in hundreds of cats, and spillover into animal shelter workers (see J Infect Dis: Serological Evidence Of H7N2 Infection Among Animal Shelter Workers, NYC 2016) - and a 2018 report of a severe H7N4 infection out of China - further illustrate the risks.

Hopefully we'll get more details on this latest case over the next few days.

Stay tuned. 

Vietnam: 300 Tons of ASF Contaminated Pork Sold At Markets & to Schools

 

How ASF Spreads

#19,103

In the 2 years prior to COVID's arrival, ASF (African Swine Fever) swept through China, and spilled over into other Asian countries, killing hundreds of millions of pigs (see African Swine Fever In China: Epizootic or An EpicZootic?).

While ASF doesn't pose a direct threat to human health, over the past decade it has killed somewhere between 1/3rd and 1/2 of the world's swine and poses a constant threat to spread to unaffected regions, including the United States and Canada (see USDA Enhances Domestic ASF Surveillance Efforts).

Although African Swine Fever can be transmitted directly from pig-to-pig, and can be carried by certain types of ticks, in many cases the virus has been spread by the movement of contaminated food products, animal feed or bedding, or other products to uninfected regions.

Six weeks ago, in South Korea: MAFRA Detects ASF DNA in Pig Feed Additive as Outbreaks Increase (n=18), we saw the impact of contaminated pig feed in South Korea. 

 

Over the past few years we've seen numerous reports (see here, here, here, and here) on the confiscation ASF-positive food products (see photo below) carried by travelers coming from endemic regions, at ports of entry in Taiwan, South Korea, Japan, and Australia.

The illegal importation of food products also happens at a much larger scale, as we saw in March of 2019 in USDA Statement On Seizure Of 1 Million Pounds Of Smuggled Chinese Pork.

The most recent FAO report (March 19th, 2006) shows the spread of ASF across Asia (note: China rarely reports outbreaks, despite many anecdotal reports).

The FAO's most recent update on Vietnam reads:

Viet Nam: Since the first ASF outbreak was confirmed on 19 February 2019, all provinces/municipalities have experienced outbreaks. The number of outbreaks has decreased from >6 000 outbreaks (2019) to 1 256 (2022) [reference1, reference2], and 714 in 2023 [reference3], but increased to 1 609 in 2024 [reference4]. In 2025, a total of 2 782 outbreaks have been confirmed.

Nationwide, over 1.27 million pigs have been culled, which represents more than 13-fold increase in 2025 compared to 2024. The peak of outbreaks occurred in July and August, primarily affecting small-scale farms that failed to meet biosecurity standards [reference5]. In 2026, as of 12 March, 261 outbreaks have been reported in 24 provinces/municipalities, leading to the destruction of over 14 700 pigs [reference6].

But this reflects only what is officially reported.  

Last January, it was widely reported that 120 tons of contaminated pork was about to be canned and shipped to supermarkets in Vietnam (see Supermarkets pull Ha Long canned pork after diseased meat discovery).

• Hai Phong City Police dismantled a criminal network that collected 120–130 tons of pork infected with African swine fever (ASF) and smuggled it into the Hạ Long Canned Food Joint Stock Company warehouse between mid-2025 and early January 2026.

• Approximately two tons of infected meat had been processed, deboned, and canned into finished products bearing the company's label before authorities intervened on 07 Jan 2026.

Today, Hanoi's Police has announced the arrest of 8 individuals (including meat inspectors) who supplied another 300 tons of contaminated pork to markets, with some ending up in school cafeterias. The (translated) official report reads:

Hanoi: Eight defendants indicted in connection with a ring involved in slaughtering and selling pigs infected with disease.

Previously, on March 17, 2026, the Economic Police Department of Hanoi City Police conducted an inspection of pig slaughtering operations at the slaughterhouse owned by Nguyen Thi Hien (born in 1995; residing in Ngoc Hoi, Hanoi) within the Van Phuc centralized livestock slaughtering facility (Hamlet 3, Nam Phu Commune, Hanoi City). This slaughterhouse supplies a large quantity of pork primarily to wholesale markets, local markets, and major food supply companies in the city.

The inspection revealed that Nguyen Thi Hien had slaughtered pigs infected with African swine fever. Hien and several other individuals colluded closely, forming a closed network from collecting diseased pigs in provinces such as Phu Tho and Tuyen Quang, transporting them to Hanoi, slaughtering them centrally, and distributing them to the market. In addition, the individuals conspired with some quarantine officials to bypass mandatory inspections, allowing diseased and even dead pigs to be slaughtered.

From the beginning of 2026 until now, the individuals involved have consumed approximately 3,600 pigs infected with the disease (equivalent to nearly 300 tons). This meat was distributed to wholesale markets, local markets, and sold to Cuong Phat Food Co., Ltd. This company then supplied food to several schools in Hanoi.

        (Continue . . . )

While it is possible that ASF infected (and uninspected) pigs may carry other diseases/parasites that could sicken humans, the big danger here is that the virus is easily spread through the sale and transport of contaminated pork products. 

In 2018 the FAO described ASF as:

A robust virus with a long life: The ASF virus is very hardy and can survive long periods in very cold and very hot weather, and even in dried or cured pork products.

"The movement of pig products can spread diseases quickly and, as in this case of African Swine Fever, it's likely that the movement of such products, rather than live pigs, has caused the spread of the virus to other parts of China," explained Juan Lubroth, FAO's Chief Veterinarian.

This is just the latest example we've seen of illegal activity threatening to spread agricultural and/or zoonotic diseases.  Over the past few months we've also seen:

Taiwan's Agency for Animal and Plant Health Inspection and Quarantine (AAPHIQ) has seizing illegal avian influenza vaccines

Repeated reports of `Midnight' dumping or burial of H5N1 poultry in Taiwan

Another report of smuggling of exotic birds into Hong Kong

South Korea MAFRA Investigations into Biosecurity Lapses on HPAI Affected Poultry Farms

And the recent discovery reported in the EID Journal of a Vaccine-Like African Swine Fever Virus Strain in Domestic Pigs, Thailand, 2024 - first detected in Vietnam in 2024 - which may be the product of unauthorized experimental use, a black-market vaccine, or even a lab accident.

Of course, most of these risky endeavors likely go unreported.   

For years, we've been warned that CAFOs (Concentrated Animal Feeding Operations) would lead to the next pandemic. And while that may still happen, recent trends suggest that FAFOs (`F' Around & Find Out) may be just as risky.

Cambodian MOH Announces 3rd Human H5N1 Case of 2026

 

#19,102

With thanks for the head's up from @E_A_Karlsson, we have the following announcement from Cambodia's Ministry of Health on their 3rd confirmed HPAI H5N1 human infection of 2026 - and 37th in just over 3 years -  this time involving a 3 y.o. child from Oddar Meanchey Province who was confirmed positive on March 29th.

The MOH announcement, along with the translation, follows:

Kingdom of Cambodia

Nation Religion King

Ministry of Health

Press Release

On  A case of bird flu in a 3-year-old child

The Ministry of Health of the Kingdom of Cambodia would like to inform the public that there is 1 case of bird flu in a 3-year-old boy who was confirmed to be positive for the H5N1 avian influenza virus on March 29, 2026 by the National Institute of Public Health. The patient lives in Tumnup Thmey village, Beng commune, Banteay Ampil district, Oddar Meanchey province, and there have been reports of sick and dead chickens and ducks in the village. The patient has been isolated in hospital and is receiving intensive medical care. Upon investigation, it was revealed that the patient’s home has chickens and ducks, including some sick and dead chickens, which the child had played around.

The emergency response teams of the national and sub-national ministries of health have been collaborating with the teams of the provincial agriculture departments and local authorities at all levels to actively investigate the outbreak of bird flu and respond according to technical methods and protocols, find the source of transmission in both animals and humans, and search for suspected cases and contacts to prevent further transmission in the community, as well as distribute Tamiflu to close contacts and conduct health education campaigns among residents in the affected villages.

The Ministry of Health would like to remind all citizens to always pay attention to and be vigilant about bird flu because H5N1 bird flu continues to threaten the health of our citizens. We would also like to inform you that if you have a fever, cough, runny nose, or difficulty breathing and have a history of contact with sick or dead chickens or ducks within 14 days before the onset of symptoms, do not go to gatherings or crowded places and seek consultation and examination and treatment at the nearest health center or hospital immediately. Avoid delaying this, which puts you at high risk of eventual death.

How it is transmitted: H5N1 bird flu is a type of flu that is usually spread from sick birds to other birds, but it can sometimes be spread from birds to humans through close contact with sick or dead birds. Bird flu in humans is a serious illness that requires prompt hospital treatment. Although it is not easily transmitted from person to person, if it mutates, it can be contagious, just like seasonal flu.

1/2

Address: Lot No. 80, Samdech Pen Nut Street (289)

Sangkat Boeung Kak 2, Khan Toul Kork, Phnom Penh

Phone: (+855) 23 885 970

Email: info@moh.gov.kh

Website: www.moh.gov.kh

It was over 3 years ago that an older clade of H5N1 (2.3.2.1.x) reemerged in Cambodia's population after a 9 year absence, spilling over into 6 humans in 2023, 10 people in 2024, and 18 people in 2025.

Cambodia's recent cases are due to a new reassortment of an older clade of the H5N1 virus (recently renamed 2.3.2.1e) - which appears to be spreading rapidly through both wild birds and local poultry.

Unlike the newer clade 2.3.4.4b H5Nx viruses - which have shown  much lower mortality rates in the United States - this older clade has proved fatal in about 40% of the cases reported by Cambodia since 2023.

There is currently no evidence to suggest human-to-human transmission of this H5 virus, with most cases reporting recent contact with sick or dead poultry.

While we continue to focus primarily on clade 2.3.4.4b H5 viruses in the United States, these cases remind us that there are many other iterations of HPAI H5 circulating around the globe (see Viruses: Zoonotic Implications of the Co-Circulation of Clade 2.3.4.4b and 2.3.2.1a H5N1 Avian Influenza Viruses in Nepal in 2023), each on a different evolutionary trajectory.

And only one of them has to get lucky to made it a very bad day for the rest of us.

(France ANSES) Vaccinating Ducks Against Avian Influenza: Lessons Learned From the First Six Months

 

#19,101

After years of increasing agricultural losses from avian influenza, many poultry farmers are understandably anxious for permission to protect their flocks with HPAI vaccines, yet most countries have been slow to embrace that strategy.

This hesitancy is based on mixed results seen in countries where AI vaccination has been adopted, and concerns over how vaccination might affect international trade.

While we've seen some impressive success stories (see OFID: Avian H5, H7 & H9 Contamination Before & After China's Massive Poultry Vaccination Campaign), we've also seen some significant failures (see J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China), often due to poorly designed and/or applied vaccines.

The biggest concern is that a vaccine that is only partially effective may merely mask the symptoms of infection, but still allow the virus to spread stealthily and continue to evolve (producing vaccine-induced escape mutants).

Eleven months ago, in NPJ Vaccines: Impact of Inactivated Vaccine on Transmission and Evolution of H9N2 Avian Influenza Virus in Chickens, a report warned that inactivated vaccines have failed to prevent - or even reduce - H9N2 in China's poultry, and may have driven viral evolution (including mammalian adaptations).

Which is why most countries - including the United States, Canada and the UK - have yet to authorize HPAI poultry vaccines, although many are studying the matter (see UK Defra Announces New Avian Influenza Vaccine Trials Begin in UK).

France, however, was an early adopter in Europe, and in the summer of 2023 announced their intention to begin vaccinating high risk poultry (ducks) against H5N1 that fall, after testing showed a two-dose regimen provided adequate protection.

Within months, however - after several breakthrough infections - the French MOA Ordered 3rd Vaccine Dose For High Risk Ducks.

Last December, the Journal Vaccine carried a study which looked at the effectiveness of the French vaccination campaign. 

To what extent may the duck population be protected after vaccination against highly pathogenic avian influenza? Contributions from a modelling approach and French field data

M. Salines a, M. Andraud a, A. Scoizec a, A. Schmitz b, E. Niqueux b, A. Jimenez Pellicer c, K. Bucher c, G. Gerbier c, N. Eterradossi d, B. Grasland b, S. Le Bouquin a

https://doi.org/10.1016/j.vaccine.2025.127905 

Earlier this month the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) published their own summary and analysis; reporting that less than half of the duck population was adequately protected at any given time. 

Vaccinating ducks against avian influenza: lessons learned from the first six months

(Excerpt)

Good overall compliance with the vaccination protocol

The main takeaway of the analysis was that the vaccination protocol was widely implemented over the period in question. Between 1 October 2023 and 31 March 2024, 51 million doses were administered, covering over 95% of duck flocks. Most of them received two doses – the first when the animals were around 10 days old and the second approximately 20 days later – in accordance with the vaccination protocol in force at the time.

The data collected were fed into a model assessing how well the ducks were protected against avian influenza. “The model showed that 40 to 45% of the duck population could be considered protected by a complete vaccination scheme at a given time, which means they’d received all the doses required for optimum vaccine efficacy and that this efficacy hadn’t yet declined”, explains Morgane Salines, a scientist in ANSES's Epidemiology, Health and Welfare (EPISABE) unit and the main author of the study.

The rest of the duck flocks only had partial protection, either because their vaccination protocol was in progress or because their immunity was declining. Indeed, experimental estimates indicated that vaccine protection declined in ducks over the age of 10 weeks. “These percentages of fully or partially protected farms can ensure a certain level of protection for the duck population as a whole. Proper vaccination compliance by production sectors is essential to optimise this protection”, adds Salines.

While vaccination helped to reduce the burden of H5N1, it did not eliminate it. ANSES goes on to warn that:

Even with good vaccination results, control and surveillance efforts must be maintained

In the winters of 2023-2024 and 2024-2025, the number of avian influenza cases on farms fell sharply compared with previous years. This decrease can be attributed both to vaccination and to the reduced circulation of the virus in wild birds. 

“Currently, avian influenza is circulating more actively in wild birds than in the winter of 2024-2025”, underlines Grasland. “More than 40 instances of the virus being introduced into French farms from wild birds have been recorded since the start of the 2025-2026 season.

In addition to vaccinating ducks, it’s important to continue implementing biosecurity measures – which prevent the virus from entering farms – and monitoring the virus, to prevent it from circulating at a low level. The goal is to ensure that the virus doesn’t develop mutations that could ultimately allow it to evade vaccination-induced immunity”. 

As a reminder, avian influenza can, under certain conditions, be transmitted to humans. Reassortment between an avian influenza virus and a human influenza virus could potentially result in a virus that spreads more easily to people. To reduce this risk of co-infection with both types of viruses, the French National Authority for Health issues a recommendation each year, advising professionals in contact with birds to receive the seasonal influenza vaccine. 

(Continue . . . )

Last August, in Vaccine X: H5N1 Highly Pathogenic Avian Influenza Vaccination: Seroresponse of Mexican Poultry in the 2022–2024, we looked at the first two rounds of HPAI poultry vaccination in Mexico.

While seroconversion and seroprotection rates approached or exceeded 80% in many states, in the breakdown of the 20 states included in the first round, 7 (33%) scored considerably lower, with 2 states in single digits. 

The authors noted:

These limitations were evident in period one, mainly across southeastern Mexican states because they did not mount an immune response after vaccination with seroconversion and seroprotection rates less than 10 % of their population.

It is likely that some of the critical points of the vaccination plan were not fully met or were not carried out properly.

And that's the rub. 

Done right, and vaccination can be highly beneficial. Done wrong, and you could be conducting an unintentional Gain-of-Function field experiment.  

We've discussed some of the  ongoing biosecurity measures that would be required to mount a safe and effective poultry vaccination campaign (see UK Joint Taskforce Policy Paper: Vaccination of Birds Against HPAIV (bird flu), including:

• Most captive birds would likely require more than one vaccination over their lifetime, and regular testing that can differentiate infected from vaccinated animals (DIVA) would be needed to prevent `asymptomatic spread' of the virus.  

• Culling and/or quarantine would still be needed for `breakthrough' infections

• A different vaccine, schedule and testing regimen would likely be required for non-avian livestock. 

None of this would be cheap or easy, but - given the endemicity of the H5Nx virus - vaccination may still be our best option going forward.

But only if we take the time and effort to do it right.

Nature Health: York University Study on Containment scenarios for H5N1

Credit NIAID

#19,100

A number of countries have procured quantities of a pre-pandemic H5N1 vaccine for human use (United States (4.8 million doses), the UK (5 million doses), Canada  (500,000 doses) Japan (10 million doses), and the EU (initially 664,000 doses but increased last year to 27+ million doses). 

With the exception of a special release of 20,000 doses of H5N1 vaccine to Finland following their 2023 fur-farm epizootic (see Finland: MOH Announcement On Avian Flu Vaccine Availability For People At High Risk), these vaccines remain locked away, as nations debate under what circumstances, and who would receive them.

Since it is assumed that it would require two doses - given 30 days apart - to convey (likely limited) immunity, only a small percentage of the population can be vaccinated in the opening months of a pandemic.  

It is widely expected that it could take 6 months or longer before any substantial quantity of vaccine would be available to the general public (see Maggie Fox's SCI AM - A Bird Flu Vaccine Might Come Too Late to Save Us from H5N1).

We've looked at various proposals for deploying existing pre-pandemic vaccines (see CMAJ: Avian Influenza and Use of the H5N1 Vaccine to Prevent Zoonotic Infection in Canada), but no strong consensus has emerged.  

However, two groups are frequently mentioned.

• People who handle live avian influenza A(H5N1) virus in laboratory settings  
• People with ongoing contact with known infected birds or other known infected animals or their environments

Exactly how and when to pull that trigger, and how receptive people will be to taking the vaccine, are big unknowns.  

This week, Nature has published a study which considers some options on how best to contain a spillover of avian flu from poultry to humans (presumably farmers). 

 It is, alas, behind a paywall, but we do have a press release from York University to fill in the gaps. First the link to the study/abstract.

Containment scenarios for post-spillover transmission chains of avian influenza H5N1 from poultry to humans

Affan Shoukat, Chad R. Wells, Gergely Röst, Alison P. Galvani, Meagan C. Fitzpatrick & Seyed M. Moghadas
Nature Health (2026)Cite this article

Inspired by the Canadian teen who contracted H5N1 in the fall of 2024 without an obvious exposure risk (see NEJM: Critical Illness in an Adolescent with Influenza A(H5N1) Virus Infection) the authors modeled several approaches to containing a spillover to humans at a B.C. poultry farm.

Isolation of infected individuals is the first obvious step, but not every case will be symptomatic (see JAMA Open: Asymptomatic Human Infections With Avian Influenza A(H5N1) Virus Confirmed by Molecular and Serologic Testing). 

Application of a `Tamiflu Blanket' may prevent some infections, but data on PEP (Post-Exposure Prophylaxis) is limited (see J.I.D.: Antivirals for Novel Influenza A Virus Infections), and antiviral resistant strains have been reported (see Emerg. Microbes & Inf: Oseltamivir Resistant H5N1 (Genotype D1.1) found On 8 Canadian Poultry Farms).

Reactive vaccination - performed after the outbreak has occurred - is hampered by the 30-40 days it takes to build immunity, whereas pre-emptive vaccination of high risk individuals (i.e. famers) negates that concern.

The authors write:

. . .  reactive vaccination has very limited additional benefits outside of self-isolation, but pre-emptive vaccination adds substantial additional benefits on top of self-isolation. 

I've reproduced some excerpts from the press release below. Follow the link to read it in its entirety.  I'll have a bit more after the break. 

Researchers model how to contain Avian flu H5N1 in case of human-to-human transmission

By Sandra McLean
March 27, 2026

At this point, Avian flu H5N1 is thought to have very limited ability to transmit between humans, but a recent case in British Columbia with an unknown source of transmission has piqued the curiosity and concern of scientists, including York University Professor Seyed Moghadas.

Did this lone case come about through transmission from an animal or another person, and if it was via human transmission, what methods will control its spread in the human population? Director of York’s Agent-Based Modelling Laboratory in the Centre of Excellence in AI for Public Health Advancement, Moghadas and a group of researchers used modelling to understand the best spread control measures should human-to-human transmission become possible.

“The idea was, let's evaluate some of the interventions that we usually implement at the very earliest stage of a disease outbreak or emerging disease, which we know very little about,” he says.

For the research, "Containment Scenarios for Post-Spillover Transmission Chains of Avian Influenza H5N1 from Poultry to Humans,” published today in Nature Health, various scenarios from isolation to vaccination before or after a spillover event were modelled. It is one of only a few studies that have explicitly modelled outbreak dynamics following spillover into humans or the effectiveness of public health interventions in early and highly uncertain phases of virus development.

(SNIP)

The researchers used Abbottsford, B.C. as the location as it is a highly dense poultry farming area. The starting point is after a spillover has happened. 

“If a human became infected, how do we block this single individual to trigger a large outbreak? Or if the infection is going on between humans, can we block these chains and to what degree we can block them?” asks Moghadas. “What is the effectiveness of either self-isolation of symptomatic cases or vaccination of farmers or vaccination of farmers and their household members?”

Even with mitigation measures, someone in the farmer’s family could potentially be infected by the farmer and then transmit it to someone in the community.

The team evaluated two different types of vaccination strategies. One was reactive, which means that you trigger a vaccination program after a case has been identified somewhere. The second strategy was pre-emptive – individuals, such as farmers, are vaccinated before any case is identified.

What they found is that reactive vaccination has very limited additional benefits outside of self-isolation, but pre-emptive vaccination adds substantial additional benefits on top of self-isolation.

Should the virus be confirmed to be capable of human-to-human transmission, Moghadas says they want to limit the chain of transmission and minimize the risk of evolution of the virus to become more adapted to human conditions. For now, he says, when cases are identified, the person should self isolate immediately. For the authorized vaccine, it should be meted out quickly to target populations, but that could take several weeks to have population level effectiveness.

“Timely action is a critical part of controlling the spread. Self-isolation of symptomatic cases has a significant effect, but that comes with the caveat that we don't know if everybody who is infected will develop symptoms,” says Moghadas.

“There could be potential asymptomatic cases we don't identify and by the time we do identify them, they've been already infecting others in the chain of transmission. This case in B.C. was particularly concerning because they could not find the source of infection.”

(Continue . . . )

There are obviously some formidable barriers to a pre-emptive vaccination campaign of farmers (poultry, and in some places, dairy) and their household contacts.   

• Existing vaccine supplies are quite limited, and an argument could be made that vaccine supplies should be reserved for `essential workers' (e.g. lab workers, HCWs, military, etc.) after an outbreak occurs. 

• Getting farmers to take the seasonal flu vaccine to prevent `reverse zoonosis' or worse - a co-infection with seasonal and zoonotic influenza - has been a challenge (see Canada: BC Provincial Health Officer Urges People Living/Working On Poultry Farms To Get Seasonal Flu Vaccine).

• Only 1 in 3 Canadians age 18-64 got the flu shot last year. It seems likely that an H5N1 vaccine would be an even harder `sell', particularly before any  outbreak has happened. 

• Farmers and governments may shy away from any program that hints that the food supply may be contaminated or unsafe, and `paralysis by analysis' may further delay any decisions. 

Despite its advantages, it seems likely that something would have to substantially elevate the public's - and the government's - level of concern before a pre-emptive vaccine program could be successfully launched. 

California: SLO County Reports Dead Sea Lion From H5N1

 
California Marine Mammals with H5N1

#19,099

Just over a month ago the Año Nuevo Natural Reserve in San Mateo County, CA announced the first U.S. detection of H5N1 in Elephant Seals after dozens of seals were observed either sick or dying and the virus was confirmed by the USDA’s NVSL lab.

Since then, according to local news outlets (see CIDRAP report), the number of HPAI positive seals has increased, along with an H5 positive otter and a sea lion. The actual count is likely much higher, as only a limited number of mammals have been tested.

In early March we saw an update and health advice from California's DPH and just over a week ago a paper on the impact of HPAI H5 on pinnipeds (see UC Davis: High pathogenicity Avian Influenza in Pinniped conservation).

Late yesterday, SLO (San Luis Obispo) county announced the discovery of a dead sea lion (H5N1 positive) on Morro Strand State Beach - some 150 miles south of the first outbreak - in the following press release.

Deceased Sea Lion Found in San Luis Obispo County Tests Positive for H5N1 (Bird Flu)

Author: Public Health
Date: 3/27/2026 2:07 PM

While the risk of H5N1 to the public remains low, officials ask community members and visitors to avoid approaching marine mammals and seabirds and report them instead through the appropriate channels. En español

San Luis Obispo, Calif— A deceased sea lion found along Morro Strand State Beach has tested positive for H5N1 (avian influenza or bird flu), marking the first confirmed case in a marine mammal in the county.

While the risk of H5N1 to the public remains low, officials from San Luis Obispo County Public Health Department, the California Department of Fish & Wildlife, and the Central California Marine Animal Response Team urge community members and visitors to avoid approaching marine mammals and seabirds. This is especially important for animals that appear sick, injured, or deceased.

“Staying 150 yards away from all marine mammals and seabirds; keeping children and pets away from sick, injured or dead wildlife; and not approaching, touching or attempting to assist marine mammals or seabirds,” states guidance from the California Department of Public Health.

Officials ask the public not to touch or help wildlife and instead to call: 

• NOAA West Coast Marine Mammal Stranding Hotline at (866) 767-6114  for assistance with marine mammals
• California Department of Fish and Wildlife at 916-358-2790 for assistance with birds

“While the risk to the public remains low, it’s understandable that people may have questions about their own health if they find themselves unexpectedly exposed to a sick or dead animal,” said County Health Officer, Dr. Penny Borenstein. “If community members have questions about H5N1 as it relates to human health, our Public Health Department can help answer those questions.”

Community members can reach the County of SLO Public Health Department by calling 805-781-5500. To learn more about H5N1 in California by visiting the California Department of Public Health’s bird flu webpage or by reading updates from UC Davis regarding recent H5N1 activity in marine mammals.

History of bird flu in SLO County

Positive cases of bird flu have been found in SLO County since 2022 from various wild birds within the county. In 2024, many states, including California, experienced outbreaks of H5N1 in dairy cattle. There were 38 confirmed human cases in California linked to exposures from infected cattle between September 2024 and January 2025 with none in SLO County.

UC Davis maintains an H5 Influenza A Outbreak in Marine Mammals webpage which now lists 28 Elephant Seals, 2 Sea Lions, and 1 otter as having tested positive in California over the past 6 weeks.

Compared to what we've seen in South America, this remains a small outbreak, but it is likely we are only seeing the tip of the iceberg. Many animals may have died unnoticed at sea, or have washed up on remote beaches. 

Although H5N1 has yet to crack the `transmission code' in humans, evidence suggests marine mammals may be closer to achieving sustained transmission (see Preprint: Massive outbreak of Influenza A H5N1 in elephant seals at Peninsula Valdes, Argentina: increased evidence for mammal-to-mammal transmission).

While that would be a terrible thing for marine mammals, it might not work out too well for us, either.