Emerg Microbes & Inf: Antiviral Activities of Multiple Antivirals Against HPAI H5N1 in Vitro and in Mice

CDC Influenza Antiviral Medications: Summary for Clinicians - Jan 2026

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For Americans (and indeed, for much of the world), our first line antiviral against severe influenza is oseltamivir (aka `Tamiflu'), an antiviral which was developed in the late 1990s.

There are other options (e.g. inhaled zanamivir, or 1-dose oral baloxavir, etc.), but they are not only more expensive, they are in far shorter supply. While the U.S. government doesn't release exact numbers, oseltamivir reportedly makes up well over 90% of all (SNS) stockpiled influenza antivirals.

None of these drugs are a panacea against influenza infection, but they are expected to reduce the severity and duration of infection; assuming they can be delivered to the patient in the first 24-48 hrs of infection.

How well they might work against a pandemic avian flu strain, like H5N1, isn't really known, particularly the standard 5-day (B.I.D) treatment course of oseltamivir or the 1-dose treatment with Baloxavir.  

We've seen concerns raised over the effectiveness of oseltamivir, including a year ago in St. Jude Researchers: Current Antivirals Likely Less Effective Against Severe Infection Caused by Bird Flu in Cows’ Milk; excerpt below:

Our evidence suggests that it is likely going to be hard to treat people severely infected with this bovine H5N1 bird flu strain,” said corresponding author Richard Webby, PhD, St. Jude Department of Host-Microbe Interactions. “Instead, reducing infection risk by not drinking raw milk and reducing dairy farm workers’ exposures, for example, may be the most effective interventions.”

“In general, baloxavir [Xofluza] caused a greater reduction in viral levels than oseltamivir [Tamiflu], but neither was always effective,” said first author Jeremy Jones, PhD, St. Jude Department of Host-Microbe Interactions.

Last January, in Nature Comms: Oseltamivir and Baloxavir Monotherapy and Combination Therapy Efficacy Against Clade 2.3.4.4b A(H5N1) Influenza Virus Infection in Ferrets, we saw a CDC study which looked at both mono and combination therapy with oseltamivir and baloxavir in ferrets infected with H5N1 (genotype D1.1).

In short, they found:

• Ferrets infected with H5N1 D1.1 and treated with oseltamivir saw little or no clinical or virologic benefit compared to no treatment, with persistent high fevers, weight loss, and systemic viral replication.
• Ferrets treated with Baloxavir saw significantly less fever, weight loss, and viral replication. Some ferrets, however, saw a late rise in fever (after 4 days) and viral shedding, suggesting a viral rebound. 
• Ferrets treated with both drugs saw similar clinical protection to baloxavir alone, but did not show signs of rebound. 

Note: Ferrets are a good, but not perfect, proxy for humans in influenza research, so these results may not be 100% applicable to humans.  

A month later, we looked at a study (Nature Comms: Baloxavir outperforms oseltamivir, favipiravir, and amantadine in treating lethal influenza A(H5N1) HA clade 2.3.4.4b infection in mice) by Webby & Jones et al. which suggests that baloxavir outperforms oseltamivir, favipiravir, and amantadine in treating clade 2.3.4.4b (circa 2022) H5N1 avian viruses (in mice).

 

All of which brings us to a new study which raises additional doubts on the effectiveness of oseltamivir monotherapy against HPAI H5.

This is a lengthy, and technically dense, study. While many will want to read it in its entirety, the bottom line is that the existing 5-day course of oseltamivir appears inadequate to treat severe HPAI H5N1 infection (at least, in mice). 

The author report Baloxavir as being more potent, but even a 5-day B.I.D course (10 times the current dose) only saved 16.7% of treated mice.  Extending treatment to 7 days (14 doses), raised survival to 50%. 

While a 7-day course of Baloxavir (BMX) was strongest single-drug therapy, extended courses of MNP+BXM and OSP+BXM provided the most effective treatments.

Before everyone freaks out, due to their higher metabolic rate, the half-life of baloxavir is much shorter in mice than in humans. While it remains to be determined, an equivalent dose in humans might be more like 2 or 3 doses spread out over a week's time. 

First the link, abstract, and a brief excerpt. I'll have a bit more after the break.

Antiviral activities of multiple antivirals against highly pathogenic avian influenza A H5N1 in vitro and in mice

Danlei Liu ,Yujing Fan,Ka-Yi Leung,Ruiqi Zhang,Hoi-Yan Lam,Xiaochun Xie,Honglin ChenORCID Icon,Kwok-Hung Chan &Ivan Fan-Ngai Hung 

Article: 2645843 | Received 28 Jul 2025, Accepted 12 Mar 2026, Published online: 31 Mar 2026

https://doi.org/10.1080/22221751.2026.2645843 

ABSTRACT

In 2024, a bovine H5N1 strain was first isolated from dairy cows in Texas and confirmed to transmit cross-species to humans. Therefore, research on treatments for human infection should be accelerated.

In our study, the antiviral effects of baloxavir acid (BXA), oseltamivir carboxylate (OSC), EIDD-1931 (NHC), and ribavirin (RBV) against five H5N1 strains were evaluated in vitro. 

Cell viability and viral replication were measured to assess the antiviral effects. The results showed that the EC50 of BXA treatment was the lowest. The BXA/NHC and BXA/OSC combination treatments showed more potent inhibitory effects than each monotherapy. The 15 mg/kg baloxavir marboxil (BXM) / 125 mg/kg molnupiravir (MNP) and the 15 mg/kg BXM / 10 mg/kg oseltamivir phosphate (OSP) were tested in BALB/c mice. 

The mice were inoculated with 10 times the 50% mouse lethal dose (10 MLD50) of bovine H5N1 virus. Treatments began 1-day post-infection (1 dpi) and were administered orally twice daily for 5 or 7 days. Changes in body weight, clinical signs, and survival were monitored; lung and brain tissues were collected for virological, immunological, and histological analyses. Most mice died from severe neurological symptoms. 

Compared with the 5-day treatment, the 7-day treatment effectively inhibited viral replication and increased survival rates to 50% in BXM, BXM/MNP, and BXM/OSP treatments. Mice treated with BXM/MNP or BXM/OSP combination therapy showed lower viral yields in the lungs than those treated with BXM alone. The results provide a reference for human treatment, and extending the 7-day combination treatment should be considered.

        (SNIP)

In summary, BXA, NHC, OSC, and RBV can significantly inhibit the replication of various H5N1 viruses in vitro. The combination treatments of NHC/BXA and OSC/BXA showed stronger antiviral effects. In mice, the 7-day BXM, MNP/BXM, and OSP/BXM treatments significantly increased survival rates.

Combination treatments significantly suppressed the viral replication in both the lungs and brains of mice. Therefore, extended BXM-based combination therapies could be considered as a first-line treatment for humans. The results provided a reference for clinical treatment.

        (Continue . . . )

 

Over the past couple of years we've seen increased calls for a shift in pandemic antiviral strategy towards Baloxavir (or combination therapy), but most countries have invested heavily in oseltamivir, making any change likely slow in coming.

Baloxavir is made only by Roche/Shionogi plants, while oseltamivir is now a generic drug manufactured around the world. The global supply of oseltamivir is probably 50 times greater than baloxavir, while the cost is roughly 1/10th.

The reality is, even oseltamivir will be hard to get - at least during the first critical first 24-48 hrs of infection - during a severe global influenza pandemic. It seems likely that `extended'  baloxavir or combination therapy will be limited to hospitalized patients with severe disease. 

Given our limited supply of antivirals and an expected wait of least 6 months before having any large quantities of vaccine, we will once again have to rely heavily on preventing infection; wearing face masks, hand washing, improved indoor ventilation, staying home while sick, and avoiding crowds.

Which is why I've already got my supply of masks, hand sanitizer, and OTC meds in the hall closet, and have stayed current with all of my vaccines.

If you aren't similarly prepared, you may want to revisit:

#Natlprep 2025: Personal Pandemic Preparedness

EID Journal: Tropism and Replication Competence of Cattle Influenza A(H5N1) Genotype B3.13 Virus in Human Bronchus and Lung Tissue

Flu Virus binding to Receptor Cells – Credit CDC

#19,107

Over the past 2 years we've seen 2 new genotypes of H5N1 emerge in North America  - `Bovine' B3.13 and D1.1 - both of which have infected thousands of  cattle, dozens of humans, and a huge (and largely uncounted) number of birds. 

While neither of these viruses have evolved into an easily transmissible strain, both have shown evidence of mammalian adaptation.  

Human cases have ranged from mild or asymptomatic (see JAMA Open: Asymptomatic Human Infections With Avian Influenza A(H5N1) Virus Confirmed by Molecular and Serologic Testing) to severe and even fatal (see Louisiana Department of Health Announces 1st H5N1-related Fatality).

Recent studies and preprints (using a variety of lung explant cultures, lung organoids, and human nasal epithelial cells) have found these new genotypes appear to be better adapted to the human respiratory system than older strains. 

A few recent examples include: 

Preprint: Bovine-derived Influenza A virus (H5N1) Shows Efficient Replication in Well-differentiated Human Nasal Epithelial Cells Without Requiring Genetic Adaptation

J.I.D.: Avian influenza virus A(H5N1) genotype D1.1 is better adapted to human nasal and airway organoids than genotype B3.13

Pre-Print: A Cattle-derived Human H5N1 Isolate Suppresses Innate Immunity Despite Efficient Replication in Human Respiratory Organoids

While these studies utilize different methods and materials, they have constantly painted a picture of the recent emergence of a more `mammalian adapted' HPAI H5 viruses. 

To that list we can add a dispatch, published this week in the EID Journal by researchers from the University of Hong Kong and St. Jude Children's Hospital, which looks at two cattle derived H5 strains (from Ohio & TX) of the B3.13 genotype in human bronchus and lung ex vivo explants.

While today's study doesn't explicitly test the D1.1 genotype, they make note of previous studies (see above) which suggest - in some ways - it may be even better adapted than B3.13.

While relatively brief, much of this dispatch is technical in nature, and those with a keen interest will want to read it in its entirety.  

This study compares B3.13 to 3 other viruses; a Clade 0 H5N1 virus (Hong Kong 1997), an aggressive H5N6 isolate from China (2014), and a 2009 H1N1 virus from Hong Kong. Briefly, they report:

• Bovine H5N1 genotype B3.13 shows partial adaptation to human respiratory tissue. 

• B3.13 replicates in lung tissue on par with the 2009 H1N1pdm virus, albeit lower in the bronchus than either H1N1pdm and H5N6.

• Receptor binding tests suggest better adaptation to α(2–6)-linked SA, compared to the early H5N1 virus.

• B3.13 induced proinflammatory responses, but far less than avian H5N1 or H5N6, which likely accounts for its relatively mild presentation.

The link and some excerpts from today's study follow.  I'll have a bit more after the break.

Dispatch

Tropism and Replication Competence of Cattle Influenza A(H5N1) Genotype B3.13 Virus in Human Bronchus and Lung Tissue

Kenrie P.Y. Hui, John C.W. Ho, Ka-Chun Ng, Richard J. Webby, Malik Peiris, John M. Nicholls, and Michael C.W. Chan  

Abstract

In 2024, influenza A(H5N1) genotype B3.13 viruses emerged from cattle and caused mild spillover infections in humans. Using human bronchus and lung tissue, we evaluated tropism, replication, and pathogenesis of 2 cattle influenza isolates.

Those viruses showed moderate replication competence and induced robust proinflammatory responses, suggesting potential risk for human health.

 

Highly pathogenic avian influenza (HPAI) H5N1 viruses remain a major global health concern, particularly because of sporadic spillover into mammals (1). HPAI A(H5N1) clade 2.3.4.4b viruses entered the United States through a trans-Atlantic introduction in late 2021, after which extensive reassortment among migratory birds produced the B3.13 and D1.1 genotypes. Those variants have spread widely, driving outbreaks in livestock and causing occasional human infections (2,3).

Beginning in 2024, H5N1 clade 2.3.4.4b viruses were detected in dairy cattle across multiple US states, and those infections were linked to mild zoonotic cases in humans (4,5). To assess the health risks of emerging cattle-origin influenza viruses, we examined tropism, replication, receptor use, and innate immune responses of cattle H5N1 viruses in human respiratory tract explants.

        (SNIP) 

Conclusions

Viral titers and influenza NP-positive cells demonstrated that cattle-origin H5N1/439 and H5N1/98638 strains are better adapted to human upper airway tissues than avian H5N1/483 and have similar replication abilities as H1N1pdm/415742 in human lung explants.

The ability to bind α(2–6)-linked SA further indicates a shift of receptor affinities that are more compatible with upper respiratory tissues. Innate immune responses of H5N1/439 and H5N1/98638 viruses in human lung tissue fell between those triggered by H1N1pdm/415742 and H5N1/483 viruses, indicating that cattle H5N1 viruses could pose a human health risk.

Defining how these strains infect human tissues and shape immune responses is critical for anticipating outbreaks and reducing zoonotic transmission risks. Because influenza viruses continually evolve across diverse avian and mammalian hosts, sustained research and surveillance remain essential to prevent human infections.

Dr. Hui is an assistant professor in the School of Public Health at the University of Hong Kong, China. Her research interests include risk assessment, understanding the pathogenesis of emerging respiratory viruses, and the development of therapeutic options for severe influenza diseases and coronavirus infections.

       (Continue . . . )
 

While it appears that neither B3.13 or D1.1 currently have the ability to spark a pandemic, H5N1 continues to set new records in infecting mammalian hosts (see ISIRV: Update on H5N1 Panzootic: Infected Mammal Species Increase by Almost 50% in Just Over a Year).

These genotypes won't be the last iterations of H5N1, and while the future trajectory of HPAI is unpredictable, recent trends should give us pause.

And if we get lucky - and HPAI H5 should prove incapable of making that evolutionary leap - rest assured there's no shortage of other viral contenders in the wild. 

Taiwan CDC Update: Novel H7 Infection Identified as H7N7

 

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We've an update this morning from Taiwan's CDC on yesterday's report (see Taiwan CDC: Human Infection with a Novel H7 Avian Virus) which identifies the novel virus as LPAI H7N7 and announces the recovery and discharge from the hospital of the patient. 

While this appears to be an isolated incident, this is a reminder that nature's laboratory is open 24/7, and new threats can emerge at any time.

Today's (translated) announcment follows:

The first locally transmitted case of H7 novel influenza A in China, whose sputum gene sequencing results identified H7N7, has been released from isolation today and is recovering at home.
 
Release Date: 2026-04-03

The Taiwan Centers for Disease Control (CDC) announced today (April 3) that the first case of local human infection with the H7 subtype of novel influenza A, which was detected recently, has been cured and discharged from isolation today after clinical treatment. The patient's condition has continued to improve and all tests have been negative. The patient will continue to be monitored until April 6.

The Taiwan Centers for Disease Control (CDC) stated that the sputum sample collected from the case on March 27th was genetically sequenced to identify the virus as H7N7, a low-pathogenic avian influenza virus (LPAI). No drug-resistant mutations were found, and the virus remains sensitive to antiviral drugs; the public need not panic. The CDC also today, in accordance with the International Health Regulations (IHR), notified the World Health Organization of this first locally acquired H7N7 influenza case through the IHR contact window.

The Taiwan Centers for Disease Control (CDC) explained that since 1959, more than 90 human cases of H7N7 have been reported globally, concentrated before 2003, mainly in Europe. Of these, only one case resulted in death, and the vast majority were mild cases of conjunctivitis. Subsequently, Italy reported three cases in 2013, also mild cases of conjunctivitis. No new human cases have been reported since 2013, but the virus continues to spread and evolve in birds.

The genetic analysis of the first H7 case in Taiwan showed that it was significantly different from the H7 cases in European human cases 10-20 years ago, and most similar to the H7 cases detected in wild birds in Taiwan over the years. No mutations related to enhanced bird-to-human transmission were found, and it is judged to be an isolated event with manageable risks.

The Centers for Disease Control (CDC) reiterates its reminder that workers in the poultry and livestock industries should adhere to disease prevention guidelines, including wearing protective equipment and proper disinfection after handling. If respiratory or eye symptoms develop, seek medical attention immediately and inform the animal contact history. The public should also follow the "5 Dos and 6 Don'ts" principle to avoid contact with or purchase poultry and livestock products from unknown sources, jointly safeguarding public health and safety. More information can be found on the CDC website (https://www.cdc.gov.tw/) or by calling the disease prevention hotline 1922. 

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

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Ask almost any paramedic, ER doctor, or ICU nurse and they will tell you that heart attacks and strokes are more common in the winter. So much so, that these events are commonly called `Christmas Coronaries’ or `Holiday Heart Attacks’.

In 1998, a study looked at the rate of heart attacks in the United States (see Seasonal distribution of acute myocardial infarction in the second National Registry of Myocardial Infarction), and found that Acute Myocardial Infarctions (AMIs) ran as much 53% higher during the winter months than during the summer.

While cold weather combined with strenuous physical activity (like clearing snow from sidewalks) has often been blamed for this spike, even in balmy Southern California, studies have shown a 33% increase in heart attacks over the holidays (see When Throughout the Year Is Coronary Death Most Likely to Occur?).

Admittedly, non-climate related factors – like overindulgence in food and drink - combined with holiday stressors like shopping, running up debt, traveling, meal preparation, and the angst that comes from dysfunctional family gatherings are all plausible contributors to this yearly spike.

But over the past 15 years studies have increasingly linked this seasonal increase in heart attacks and strokes to acute influenza and respiratory infections. A few (of many) studies include:

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

PloS One: Early Risk of Acute Myocardial Infarction Following Hospitalization for Severe Influenza

JAHA: Another Study Linking ILI To Increased Risk Of Heart Attack & Stroke

PLoS One: Transient Depression of Myocardial Function After Influenza Virus Infection

NEJM: Acute Myocardial Infarction After Laboratory-Confirmed Influenza Infection

Eur. Resp.J.: Influenza & Pneumonia Infections Increase Risk Of Heart Attack and Stroke

At the same time, we've seen growing evidence that the uptake of the seasonal flu vaccine may reduce the incidence of heart attack and stroke, even if the vaccine doesn't prevent influenza infection.

Nature: Influenza Vaccination & Major Cardiovascular Risk: a Systematic Review & Meta-Analysis

The Lancet: Influenza Vaccine to Reduce Adverse Vascular Events in Patients with Heart Failure

AHA: Study Shows Flu Shots Reduce Deaths From Heart Failure

All of which brings us to a new study, published yesterday in Eurosurveillance, which seeks to confirm and expand upon these earlier findings using Danish national health records from across the 2014-2025 influenza seasons.

They found that people (age 40+) with a confirmed flu infection were more likely to be hospitalized for a heart attack or stroke in the first 7 days after testing positive. The risk was highest in the first 3 days, and returned to normal after 2 weeks. 

Intriguingly, they found the short-term risk was reduced by about 50% among those with a positive influenza test, but vaccinated.  

Today's study is quite detailed, and many will want to read it in its entirety. I've only reproduced the link, and summary, followed by a link to an accompanying editorial. 

I'll return with a brief postscript about an unexpected finding after the break.  

Influenza vaccination attenuates acute myocardial infarction and stroke risk following influenza infection: a register-based, self-controlled case series study, Denmark, 2014 to 2025  
Roberto Croci1,2,* , Johanna J Young2,* , Hanne-Dorthe Emborg2 , Palle Valentiner-Branth2 , Steen Ethelberg2,3 , Christian Holm Hansen2 

What did you want to address in this study and why?

Catching influenza increases the short-term risk of heart attack and stroke. Influenza vaccination has been shown to reduce this risk by preventing infection, but it is unclear whether it also offers protection among people who become infected despite vaccination. We wanted to quantify how much more at risk of heart attack and stroke adults in Denmark are shortly after catching influenza, and to assess if prior vaccination can attenuate this risk.

What have we learnt from this study?

In adults 40 years or older in Denmark, hospital admissions for heart attack and stroke were more frequent in the first week after testing positive for influenza than during any other period in the year before and after their test, almost threefold for stroke and fivefold for heart attack. This increased risk was about half as high among people who tested positive for influenza but had received the influenza vaccine that season.

What are the implications of your findings for public health?

Influenza vaccination may offer cardiovascular protection even in instances when it does not prevent infection. If confirmed by additional studies in other settings, this would strengthen the case for prioritising influenza vaccination among people at risk of heart disease or stroke and would support refining recommendations across Europe.

       (SNIP)

      Conclusions

Our findings add to the evidence that influenza vaccination confers cardiovascular protection. In this study, prior vaccination halved the excess risk of acute myocardial infarction or stroke following breakthrough influenza infection. These results strengthen the case for prioritising influenza vaccination in high-risk groups. Highlighting the dual protection offered by vaccination, against both infection and its cardiovascular complications, could have a substantial public health impact. Factoring this into economic and burden analysis might improve the cost-effectiveness profile of vaccination programmes.

       (Continue . . . )

        Editorial

Does influenza vaccination protect people with breakthrough infections from acute cardiovascular events?
Jeffrey C Kwong

Of note, the authors of this study used a (bacterial, non-respiratory) laboratory-confirmed Campylobacter spp. infection as a negative control group, and found a similar increase in cardiac risk to influenza infection.   

Unlike with influenza, previous flu vaccination showed no attenuating effect. 

They wrote:

Unexpectedly, infection with Campylobacter spp., a food-borne, non-respiratory bacterial pathogen, was associated with a threefold increase in acute cardiovascular events.

One explanation may be that any infection severe enough to warrant microbiological testing can result in proinflammatory events. Alternatively, unmeasured respiratory co-infections might have determined the risk increase, at least in part.

Meta-analyses have shown that respiratory pathogens other than influenza can trigger acute cardiovascular events [24]. Research should clarify whether this is true for non-respiratory pathogens as well. Importantly, the absence of effect modification by influenza vaccination in our Campylobacter-negative exposure analysis reinforces that the observed risk attenuation after influenza infection is exposure-specific. 

While cardiac complications have been reported following Campylobacter infection (see Review of Campylobacter Species Related Cardiac Disease), today's findings suggest this may be more common than previously believed.

Although the current flu vaccine is nowhere near as effective as we'd like it to be, and the promise of a universal flu vaccine remains elusive (see J.I.D.: NIAID's Strategic Plan To Develop A Universal Flu Vaccine), we continue to see evidence that the benefits of vaccination may extend beyond simply reducing the risk of influenza infection. 

Which is why I'll be rolling up my sleeve this fall for both the Flu and COVID vaccines. Because at my age - and in my physical condition - I can use all the advantages I can get. 

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

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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.

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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.