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

 

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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 

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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

 
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

 
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.

        (Continue . . .) 

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

#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

 
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.”

        (Continue . . . )

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.

(Continue . . . )

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

#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. 

1. 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). 
2. The fatal H5N1 case in Cambodia was hospitalized on April 16th, but was only confirmed H5 positive on April 21st (died on the 22nd).
3. 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.