#Cattle and #human #organoids reveal 2.3.4.4b #H5N1 cross-species #transmission potential and #neuraminidase-specific neutralizing #antibodies in humans

 

Abstract

The unexpected circulation of clade 2.3.4.4b H5N1 influenza viruses in dairy cattle and the transmission to diverse mammalian species poses a pandemic risk. We sought to explore cattle and human respiratory susceptibility to the 2.3.4.4b H5N1 virus. We establish long-term expandable cattle airway and mammary organoids. The 2.3.4.4b H5N1 virus exhibits high replicative fitness in cattle mammary organoids, recapitulating its remarkable mammary tropism. The virus also replicates robustly in cattle airway organoids, suggesting an underrecognized respiratory component in ongoing outbreaks. Interestingly, human airway and nasal organoids are highly susceptible to the 2.3.4.4b H5N1 virus. Yet, a novel organoid-based neutralization assay reveals that N1 antibodies in human sera had cross-neutralizing activity against the 2.3.4.4b H5N1 and ancestral H5N1-VN1194 viruses. The cross-neutralization, exclusively manifested in the organoid-based assay, is enhanced after seasonal influenza vaccination and diminished after depleting N1-specific antibodies. Therefore, cross-neutralizing N1 antibodies are likely limiting zoonotic infection by H5N1 viruses in humans.

Source: 

Link: https://www.nature.com/articles/s41467-026-74345-w

____

Characterization of #oseltamivir-resistant #H5N1 clade 2.3.4.4b, genotype #D1.1 #variants identified in #poultry farms of British Columbia, #Canada

 

ABSTRACT

Highly pathogenic avian influenza A(H5N1) viruses of clade 2.3.4.4b, genotype D1.1, are responsible for widespread outbreaks in poultry and continue to cause sporadic, sometimes severe, human infections. Herein, we characterized a wild-type (WT) influenza A(H5N1) D1.1 isolate (BC-H5N1-WT) and its H275Y neuraminidase (NA) variant (BC-H5N1-H275Y), both of which emerged on farms in British Columbia, Canada, during the fall 2024 outbreak. In vitro analysis assessed replication kinetics in MDCK cells, with supernatants collected at different days post-infection (p.i.) and titrated by TCID50 and qRT-PCR. Neuraminidase inhibitor (NAI) susceptibility was determined by NA inhibition assays, whereas susceptibility to baloxavir acid (BXA) was evaluated by plaque reduction assay. In vivo virulence was evaluated in BALB/c mice infected with serial 10-fold dilutions of each virus to monitor weight loss and mortality. Viral titers in lungs, brain, nose, kidney, spleen, and heart were quantified at day 4 p.i. The BC-H5N1-WT virus was susceptible to the four antivirals tested, whereas BC-H5N1-H275Y displayed resistance to oseltamivir and peramivir but remained susceptible to zanamivir and BXA. The BC-H5N1-WT exhibited significantly higher viral replication titers than BC-H5N1-H275Y at all tested time points and showed larger plaque sizes. In mice, BC-H5N1-WT was more virulent with LD50 values of 1.78 × 103 PFUs compared to 8.71 × 104 PFUs for BC-H5N1-H275Y, and produced higher viral titers in lungs and other organs. Despite the reduced fitness of the resistant H5N1 D1.1 variant, its emergence in the absence of viral selection pressure underscores the need for continued surveillance.

Source: 

Link: https://www.tandfonline.com/doi/full/10.1080/22221751.2026.2686474

____

Inter-population #connectivity of southern elephant #seals and the likely intra-species #transmission #pathways of high pathogenicity avian #influenza

 

Abstract

High Pathogenicity Avian Influenza (HPAI) H5N1 clade 2.3.4.4b has spread beyond birds to affect seals across the Southern Ocean and sub-Antarctic region, with southern elephant seals (Mirounga leonina) particularly devastated. The virus, likely introduced via spillover from infected migratory birds, has killed tens of thousands of adult seals and pups throughout most of their range, though Macquarie Island remains unaffected so far. We used twenty years of elephant seal movement data from the southern Indian and Pacific oceans to assess whether seal-to-seal transmission could spread HPAI H5N1 between breeding colonies, despite the vast distances separating them (Marion Island, Iles Crozet, Iles Kerguelen, and Macquarie Island). There was substantial overlap in seals' at-sea distributions during their winter post-moult trips, when seals travel for weeks at average speeds of 3.5 km/h. Two transmission pathways were examined: (1) terrestrial "stepping stone" routes, where infected seals could pass the virus between colonies during short intervals to remain infectious were feasible from Marion Island to Kerguelen but not from Kerguelen to Macquarie Island; and (2) at-sea encounters between seals, which occurred frequently enough to enable transmission. The findings suggest that once established at Macquarie Island, the virus could potentially spread further to New Zealand's sub-Antarctic islands and mainland New Zealand. While seal-to-seal transmission appears possible, we conclude this is unlikely. Nonetheless, understanding at-sea contact rates enhances knowledge of H5N1 epidemiology and demonstrates the value of combining long-term population monitoring with movement data to understand wildlife disease dynamics.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Integrated Marine Observing System, https://ror.org/010x3gp67

CNRS

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.07.07.737127v1

____

#Germany - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

Three wild cygnuses of unspecified species in the Hamburg Region.

A wild Greylag Goose in the Hamburg Region.

Source: 

Link: https://wahis.woah.org/#/in-review/7688

____

First #Ecuadorian #Pediatric Case of Multisystem and #Neurological Involvement Associated with #Influenza A #H5N1 Virus—Case Report

 

Abstract

Influenza A (H5N1) is a highly pathogenic zoonotic virus with a human fatality rate of approximately 60%. Pediatric cases and associated neurological manifestations remain poorly documented in Latin America. This report describes the first confirmed Ecuadorian pediatric case of H5N1-associated encephalitis and multisystem organ failure in a previously healthy 9-year-old female following direct contact with infected poultry. The clinical course was characterized by an atypical initial presentation of bilateral periorbital edema and headache, progressing to acute encephalitis, cerebral ischemia, flaccid tetraplegia, central diabetes insipidus, and refractory septic shock. Diagnostic confirmation was achieved via nasopharyngeal RT-PCR, with additional RT-PCR and sequencing performed on cerebrospinal fluid, which identified conserved influenza A M1/M2 gene fragments, while laboratory markers—including marked elevations in IL-6, ferritin, and CRP—indicated a severe hyperinflammatory state. Management involved an intensive multidisciplinary approach utilizing oseltamivir, intravenous immunoglobulin, modulated-dose corticosteroids, desmopressin, and mechanical ventilation. Despite a severe clinical course, the patient achieved a favorable recovery, with a Glasgow Coma Scale score of 15/15 at discharge and only partial residual paresis and left hypoacusia as sequelae. This landmark case provides rare evidence of H5N1 neuroinvasion in a pediatric patient and demonstrates that timely detection combined with aggressive immunotherapy and antiviral treatment can improve survival. Furthermore, it underscores the critical necessity for strengthened regional molecular surveillance and clinical training to recognize atypical presentations of emerging zoonoses in Latin America, especially in cases involving contact with sick poultry.

Source: 

Link: https://www.mdpi.com/1999-4915/18/7/749

____

Clade 2.3.4.4b #H5N1 #influenza virus and #SARS-CoV-2 #seroprevalence among owned and feral #cats in #Philadelphia and surrounding communities

 

Abstract

Clade 2.3.4.4b H5NX influenza viruses have spread widely in birds since 2020. In addition to causing disease in birds, these viruses have infected a variety of mammals, including humans. Clade 2.3.4.4b H5N1 viruses are currently causing an outbreak among dairy cattle in the United States, and it is important to determine if other mammals have been exposed to H5NX viruses. Cats, specifically outdoor and feral cats, frequently predate wild birds. Recent studies have shown that cats living on dairy cattle farms can be infected with H5N1. Here, we completed serological studies to determine if owned and feral cats living in an urban environment in the United States have evidence of past H5N1 exposures. We used multianalyte bead-based assays to measure clade 2.3.4.4b hemagglutinin (HA) antibody levels in serum samples collected in July 2023 to June 2025 from 417 feral and 228 owned cats from the greater Philadelphia area. We also measured antibody levels against a panel of HAs from other human and non-human influenza viruses, and the receptor binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We completed additional H5N1 and SARS-CoV-2 neutralization assays using samples that had detectable antibodies in the multianalyte bead-based assays. One cat (0.16%) was positive for H5 antibodies and twenty cats (3.1%) were positive for SARS-CoV-2 antibodies in both binding and neutralization assays. These data suggest that cats in the Philadelphia area have not been routinely exposed to clade 2.3.4.4b H5N1 viruses but have been more commonly exposed to SARS-CoV-2.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.07.03.736283v1

____

#Assessment of #influenza virus and #coronavirus #tropism, #replication competence and disease severity in ex vivo and in vitro cultures of the #human respiratory tract

ABSTRACT

The emergence of animal influenza viruses circulating in poultry and human populations poses a significant public health threat, yet current risk assessment tools that connect surveillance data to human transmission risk and disease severity are lacking. To address this, we employed a semi-quantitative approach to analyze virus tropism and replication competence, conducting risk assessments of influenza and coronavirus adaptation to human transmission in an ex vivo model, and evaluating virus-induced impairment of alveolar fluid clearance (AFC) in vitro as a correlation of disease severity. Our results showed that seasonal influenza A H1N1, H3N2, influenza B, MERS-CoV, and SARS-CoV exhibited productive viral replication and tissue infection in bronchial tissues, whereas wild bird surveillance isolates such as H5N3 and H7N1 showed minimal replication when compared to pandemic H1N1 and highly pathogenic avian influenza (HPAI) H5N1. Notably, differential lung viral replication and tissue tropism were detected for H5N6 and H9N2. HPAI H5N1, H7N9, MERS-CoV, and SARS-CoV caused more severe AFC impairment than seasonal H1N1, H3N2, and influenza B viruses, correlating with their clinical severity. Overall, these findings revealed an important association between viral tropism and human transmissibility in ex vivo explants, as well as the impairment of AFC in vitro, which aligns with the clinical manifestations of disease severity across different viral strains.

Source: 

Link: https://www.microbiologyresearch.org/content/journal/jgv/10.1099/jgv.0.002281

____

#Genomic #Surveillance Uncovers the Silent #Spread of Avian #Influenza Virus #H5N1 2.3.4.4b Among Wild #Birds and #Mammals Along #Brazil’s Southern Coast

 

Abstract

Avian influenza viruses (AIVs) are widely distributed and have a wide range of hosts. Recently, the number of cases of infection associated with the circulation of highly pathogenic avian influenza H5N1 2.3.4.4b has raised concerns about its high transmission capacity in birds and mammals. This study analyzed swabs from bird and mammal species from the coast of Paraná and the northwest region of São Paulo, Brazil, for the presence of AIV in animals that did not present clinical or histopathological lesions of infection that indicated the need for molecular characterization during monitoring. Of the 661 animals analyzed, three tested positive, two of which were birds (Sula leucogaster and Thalasseus acuflavidus) while one was a mammal (Otaria flavescens) (0.45%, CI 95%: 0.16–1.33). A complete genome sequence of H5N1 AIV was obtained from a brown booby (Sula leucogaster) from the Paraná coast (GISAID accession number: EPI_ISL_1897537). Our study reinforces the importance of continuous genomic surveillance, especially in AIV hosts that do not show signs of infection, to enhance the One-Health assessment approach.

Source: Viruses, https://www.mdpi.com/journal/viruses

Link: https://www.mdpi.com/1999-4915/18/7/738

____

#Colombia - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

    As part of the epidemiological surveillance activities carried out by the Colombian Agricultural Institute, aimed at the early detection of clinical signs consistent with avian influenza, an outbreak of high pathogenicity avian influenza was confirmed in the village of Puerto Murillo, in the municipality of Puerto Carreño, Vichada Department. 

    The outbreak affects non-poultry birds in a backyard, in which digestive symptoms and mortalities were observed. 

    The National Veterinary Authority initiated screening and epidemiological monitoring efforts in the area of origin of the affected birds. 

    As a control measure, all the birds in the epidemiological unit were culled, and, in addition, epidemiological surveillance in the surrounding area was strengthened to identify other possible cases and prevent the spread of the outbreak.

    The animal health event occurred on a family subsistence farm (backyard) and affected only a flock of birds that, according to the definitions in the WOAH Terrestrial Animal Health Code, are not considered poultry, as they are intended solely for the household consumption without commercial purposes or links to livestock production chains. 

    The reported clinical picture was characterized by weakening, anorexia, profuse diarrhea, and high mortality following epidemiological contact with migratory wild birds.

Source: WOAH, https://wahis.woah.org/#/home

Link: https://wahis.woah.org/#/in-review/7674

____

#Germany - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

Laying hens and ducks in the Niedersachsen Region.

Source: WOAH, https://wahis.woah.org/#/home

Link: https://wahis.woah.org/#/in-review/7679

____

#Portugal - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

After several months without detection of HPAI circulation, these are the first outbreaks confirmed in 2026.

{Lisboa Region} Yellow-legged gull with weakness and neurological clinical signs found at a city park.

__

By Andreas Trepte - Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=723467

{Aveiro Region} Lesser black-backed gull with neurological clinical signs found at a fishing port.

Source: 

Link: https://wahis.woah.org/#/in-review/7671

____

#Australia notifies first case of High Pathogenicity Avian #Influenza #H5N1 in a wild #bird (WOAH, June 30 '26)

    On 20 June 2026, WOAH was notified of the first detection of high pathogenicity avian influenza (HPAI) H5N1 in Australia in a marine wild bird, a migratory brown skua (Stercorarius antarcticus). 

    The virus is related to H5N1 HPAI clade 2.3.4.4b viruses, which is the same subtype that is predominantly circulating in poultry, wild birds, and mammals globally. 

    Enhanced general and targeted surveillance is underway by the animal health authorities to determine the extent of infection. 

    An epidemiological investigation has commenced.

    HPAI H5N1 has caused a global panzootic since 2021, affecting wild birds, poultry, and multiple mammalian species. 

    Until recently, Australia remained free of this particular subtype despite widespread international incursions.

    Since its emergence, this H5N1 subtype has crossed continents, reaching North and South America in 2022 and extending to the Antarctic islands in 2023. 

    It has since been detected in new host species such as cattle, and marine mammals, caused sporadic human infections, driven exceptionally high activity in wild birds in 2025, and is now being reported in Australia for the first time.

    The World Organisation for Animal Health (WOAH) acknowledges Australia’s immediate notification of Influenza A virus of high pathogenicity in non-poultry birds through the World Animal Health Information System (WAHIS)   and commends Australia for its longstanding commitment to transparency and to the protection of global animal health.

    This notification represents a significant epidemiological event, documenting the first detection of HPAI H5N1 in a wild bird in Australia. 

    The finding confirms the incursion of this globally circulating virus lineage into wildlife in a subregion that had remained free from this subtype despite its extensive international spread in other regions and sub-regions. 

    The risk for Australian avifauna, especially endemic bird species is significant.

    This detection underscores critical considerations: 

        ° Early detection remains our strongest line of prevention 

        ° Early detection and timely reporting linked to early response measures, are essential in limiting the spread of HPAI and reducing its impact on poultry, livestock, wildlife, livelihoods and human health. This event demonstrates the value of sustained surveillance systems, laboratory capacity and field awareness in identifying emerging threats.

    ° Transparency and solidarity strengthen global preparedness 

    ° Timely reporting through WAHIS   allows countries to access official information, assess risks and coordinate responses based on reliable scientific evidence.  

    ° Preparedness requires sustained investment 

        Preparedness is best built before an emergency. Recent events demonstrate the cost of waiting. According to WOAH’s State of the World’s Animal Health 2026 report, more than 2,000 outbreaks of HPAI were reported by 64 countries and territories between 2025 and 2026, resulting in the loss or culling of more than 140 million poultry. At the same time, animal health continues to receive only a small fraction – 0.6% – of global health investment. Strong Veterinary Services, well-equipped laboratories, collaboration with WOAH Reference Laboratories, effective surveillance systems, trained personnel, One Health collaboration, international networks of expertise such as OFFLU and emergency preparedness plans do not emerge during a crisis – they are built through sustained investment over time.

    ° Continued national and international investment remains essential to reduce the impact of HPAI and other emerging animal health threats. 

    ° Multisectoral collaboration 

        This event also highlights the importance of maintaining strong scientific collaboration networks and engaging stakeholders before emergencies arise. Governments, Veterinary Services, laboratories, researchers, wildlife authorities, public health authorities, industry and international organisations play complementary roles in strengthening preparedness and response.  

        WOAH remains committed to supporting its Members through international standards, scientific expertise, capacity building and transparent information sharing. As HPAI continues to evolve globally, continued collaboration, preparedness and collective action remain essential to protect animal health, safeguard livelihoods and strengthen global health security. 

    ° WOAH calls on its Members to:  

        - Maintain enhanced avian influenza SURVEILLANCE  in domestic and wild birds and consider HPAI in differential diagnosis for other susceptible wild or domestic animal species.   

        - REPORT cases of HPAI in all animal species, including in domestic and wild mammals, to WOAH through its World Animal Health Information System (WAHIS)    . Genetic sequences of avian influenza viruses should be shared in publicly available databases. 

        - COLLABORATE with public health authorities, wildlife authorities and other relevant partners through a One Health approach to strengthen surveillance, risk assessment, preparedness and response.

        - CONSIDER  poultry vaccination    as a possible complementary avian influenza control measure;

        - PREVENT the introduction and spread of the disease by implementing strict biosecurity measures in poultry holdings and 

        - EMPLOY good   production and hygiene practices     when handling animal products. Relevant measures notably include keeping poultry away from contact with wild birds, ensuring good hygiene in poultry housing and equipment and reporting bird illnesses and deaths to the Veterinary Services. 

        - PROTECT humans and other potentially susceptible mammals (both wild and domestic). People in close contact or exposed to wildlife should always take   precautionary measures     to avoid getting infected and minimise the risk of mechanically carrying the virus.   

        - AVOID IMPLEMENTING unjustified trade restrictions. Import risk management measures should be scientifically justified and in line with the WOAH International Standards. 

    ° WOAH is fully committed to supporting its Members to mitigate the risks associated with avian influenza. We will continue to engage with our networks of experts, OFFLU, as well as public and private partners, notably through the One Health Quadripartite   and the Global Framework for Transboundary Animal Diseases (GF-TADs)     to provide technical updates as more information becomes available. 

    ° In collaboration with its  Reference Centres  , networks of experts and Members including the WOAH WildNet network of collaborating centres on wildlife health, the WOAH remains in close contact with Australian Veterinary Authorities to monitor the situation to assess the risks to poultry,  wildlife, other susceptible animal species and humans. Australia’s rapid detection and transparent reporting demonstrate the value of strong surveillance systems and international cooperation. As HPAI continues to evolve and spread across regions and species, timely information sharing, scientific collaboration and sustained preparedness remain essential to protect animal and public health. Transparent reporting is also critical to maintaining trust, supporting evidence-based decision-making and preventing misinformation and disinformation. 

Source: 

Link: https://www.woah.org/en/australia-notifies-first-case-of-high-pathogenicity-avian-influenza-h5n1-in-a-wild-bird/

____

#Sialic acid-anchored #haemagglutinin stalk neutralizing #antibody M-SiaB enhances #protection against highly pathogenic #influenza #H5N1/Texas/2024

 

Abstract

The recently emerged cattle H5N1/Texas/2024 strain highlights the need for effective prophylactic and therapeutic drug interventions, yet most existing neutralizing antibodies (NAbs) have limited efficacy against genetically divergent pathogenic influenza viruses. Here we engineer a sialic acid-anchored tandem M-SiaB by fusing a hemagglutinin (HA) stalk-specific monoclonal NAb with a sialic acid-receptor-binding domain (SiaB). M-SiaB shows 4- to 20-fold greater neutralizing potency against diverse authentic influenza viruses compared to the parental NAb and suppresses multiple stages of the viral life cycle, including viral attachment, entry and release. Importantly, intranasal M-SiaB confers markedly enhanced protection against nasal challenges with the pathogenic H1N1/PR8 and H5N1/Texas/2024 strains. Notably, a single dose of M‑SiaB maintains survival after a highly lethal H5N1/Texas/2024 challenge for up to 21 days. These findings demonstrate that simultaneously targeting HA stalk and sialic acid-receptor is a promising strategy to enhance the potency and breadth of NAbs against genetically divergent pathogenic influenza viruses.

Source: Nature Communications, https://www.nature.com/ncomms/

Link: https://www.nature.com/articles/s41467-026-74633-5

_____

Detection of #H5N1-Related #PB1 Sequences in a Low Pathogenic #H11N2 Virus from South #American Migratory #Shorebirds

 

Abstract

Highly pathogenic avian influenza (HPAI) A(H5N1) viruses of clade 2.3.4.4b have recently spread across the Americas, prompting intensified surveillance efforts in Brazil aimed at early detection in wild birds. As part of these efforts, we identified a low pathogenic avian influenza A(H11N2) virus in a white-rumped sandpiper (Calidris fuscicollis) sampled at Lagoa do Peixe National Park (PNLP) in southern Brazil. Whole-genome sequencing revealed that seven of the eight gene segments shared high nucleotide similarity (approximately 98.8%) with viruses previously detected in shorebirds from Delaware Bay, North America. In contrast, the PB1 segment showed high nucleotide similarity (approximately 99%) to the PB1 lineage associated with clade 2.3.4.4b A(H5N1) genotype B3.2 viruses circulating in the Americas. Phylogenetic, nucleotide identity, and molecular clock analyses indicated that this lineage shares a recent common ancestor with North American LPAI viruses and was subsequently detected in distinct viral genetic backgrounds. Although no HPAI virus was identified in this study, the presence of a PB1 segment related to H5N1-associated lineages suggests that genetic components linked to these viruses were circulating among low pathogenic avian influenza viruses in South America. These findings highlight the importance of continued surveillance in migratory bird populations to improve understanding of avian influenza virus diversity and support epidemiological monitoring.

Source: 

Link: https://www.mdpi.com/1999-4915/18/7/710

____

Avian #influenza #overview March–May 2026 (ECDC, Summary, June 26 '26)

26 June 2026

Publication series: Avian influenza overview

    

    Between 28 February and 4 June 2026, 949 highly pathogenic avian influenza (HPAI) A(H5) virus detections were reported in domestic (186) and wild (763) birds in 30 countries in Europe.

Abstract

    The downward trend in the number of detections observed at the end of the previous reporting period continued and is expected to persist throughout the summer. 

    While the number of HPAI A(H5N1) outbreaks in domestic birds remained at a low level, except in a few countries, A(H9N2) virus of clade G5.5 was detected in poultry in Europe for the first time. 

    Following the intense circulation of HPAI viruses in waterfowl in recent months, sporadic detections were reported in mammals, particularly in wild carnivores, including the detection of A(H5N5) virus in a polar bear and a walrus in Norway. 

    Outside Europe, the focus of HPAI virus detections shifted from North to South America, where a large number of outbreaks and mortality events in swans were reported. 

    Between 28 February and 4 June 2026, 19 cases of avian influenza virus infection were publicly reported in humans (including three fatal cases) in six countries and territories: Bangladesh (two cases with A(H5N1), one fatal), Cambodia (three cases with A(H5N1), one fatal), India (one case with A(H5N1)), Italy (one imported case with A(H9N2)), China (10 A(H9N2) cases and one fatal A(H5N6) case), and Taiwan (one A(H7N7) case). 

    Most human cases reported exposure to poultry or a poultry environment prior to detection or onset of illness. 

    Human infections with avian influenza viruses remain rare and no sustained human-to-human transmission has been documented. 

    The risk posed by avian influenza A(H5N1) clade 2.3.4.4b viruses currently circulating in Europe remains low for the general public in the European Union/European Economic Area (EU/EEA) and low-to-moderate for those occupationally or otherwise exposed to infected animals or contaminated environments.

Source: 

Link: https://www.ecdc.europa.eu/en/publications-data/avian-influenza-overview-march-may-2026

____

Detection of #antibodies against avian #influenza in #European dairy #cattle, the #Netherlands, January 2026

 

Abstract

In December 2025, highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b genotype DI.2.1 virus was detected in a cat living on a dairy cattle farm. Milk and serum samples from the dairy cattle were tested for avian influenza virus. No viral RNA was detected; however, H5N1-specific antibodies were identified in serum samples from 34 (47.2%) of 72 lactating dairy cows and 24 (63.2%) of 38 youngstock. These demonstrate expansion of the mammalian host range of HPAI H5N1 in Europe.

Source: 

Link: https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2026.31.25.2600464#abstract_content

____

A #bovine #H5N1 virus efficiently replicates in differentiated #human #nasal epithelial #cells

 

Abstract

Highly pathogenic avian influenza (H5N1) viruses of clade 2.3.4.4b have caused significant losses in bird populations worldwide and repeatedly infected mammals, including humans, without sustained human to human transmission. Here we show that an H5N1 virus (H5N1Tex/24) isolated from bovine milk in Texas in 2024 replicates just as efficiently in differentiated human nasal epithelial cells as a pandemic H1N1 virus strain from 2009 (H1N1HH4/09), at both 37 °C and 33 °C. The adaptive mutations PB2 M631L and PA K497R promoted replication at 33 °C but had no effect on replication at 37 °C. An H5N1 virus (H5N1BE/22) isolated from a pelican in 2022, which lacked these mutations, replicated efficiently at 37 °C but poorly at 33 °C, and this limitation was not overcome by the introduction of the PB2 M631L and PA K497R mutations. The differentiated nasal epithelial cell cultures expressed receptors for both human and avian influenza viruses. Accordingly, no HA mutations associated with altered receptor specificity were detected. H5N1Tex/24 was able to effectively suppress the production of interferon-λ, yet remained sensitive to the antiviral effects of this cytokine. These findings suggest that H5N1Tex/24 possesses intrinsic traits supporting efficient replication in differentiated human upper airway cell cultures.

Source: npj Viruses, https://www.nature.com/npjviruses/

Link: https://www.nature.com/articles/s44298-026-00208-2

____

Identification of HLA-A33-restricted #CD8+ T cell epitopes from avian #influenza #H5N1

 

Abstract

The rapid evolution of avian influenza A/H5N1, including the recent U.S. clade 2.3.4.4b outbreak, highlights its pandemic potential and the urgent need for durable, broadly protective vaccines. Given the capacity of CD8+ T cells to mediate cross-strain immunity, we investigated whether geographically distinct HLA-A33 allotypes, HLA-A*33:01 in East/Southeast Asia and HLA-A*33:03 in South Asia, differentially shape the influenza immunopeptidome and influence antiviral immunity. Antigen-presenting cells overexpressing HLA-A*33:01 or HLA-A*33:03 were transfected with single A/H5N1 antigens or infected with A/X-31 (H3N2) as a control comparison representing current seasonal influenza virus. We identified novel ligands restricted to HLA-A*33:01 (57 from A/H5N1; 55 from A/X-31) and HLA-A*33:03 (29 from A/H5N1; 45 from A/X-31). Although fewer peptides were recovered for HLA-A*33:03, a larger proportion of A/X-31-derived peptides were predicted as high-affinity binders (74%) compared with HLA-A*33:01 (61%), indicating qualitative differences in antigen presentation. To determine immunogenicity, peripheral blood lymphocytes from HLA-A*33:03-positive, A/H5N1-naïve donors were stimulated with four conserved peptides: PB2GTF, PB2KTY, NPSVQ and PB1MTK. All elicited robust CD8+ T cell activation despite the absence of prior A/H5N1 exposure, demonstrating cross-recognition by memory T cells primed against seasonal influenza. These findings define HLA-A33-restricted influenza epitopes and reveal allotype-specific presentation features that shape CD8+ T cell immunity. Conserved, immunogenic peptides identified here represent promising candidates for rational design of broadly cross-reactive vaccines to protect HLA-A33-expressing populations against severe A/H5N1 disease. Data are available via ProteomeXchange with identifier PXD078870.

Competing Interest Statement

AWP is a scientific advisor for Bioinformatics Solutions Inc (Canada), a shareholder and scientific advisor for Evaxion Biotech (Denmark), and a co-founder of Resseptor Therapeutics (Australia). These organisations had no role in the design of the study in the collection, analyses, or interpretation of data in the writing of the manuscript or in the decision to publish the results. All other authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Funder Information Declared

NHMRC, 1122099, 2016596

Source: BioRxIV, https://www.biorxiv.org/

Link: https://www.biorxiv.org/content/10.64898/2026.06.21.733083v1

____

#Australia - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

{Click on Image to Enlarge}

__

By Liam Quinn from Canada - Brown Skua landing near a penguin colony. Uploaded by Snowmanradio, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=15465669

___

    This is the first detection of H5N1 HPAI clade 2.3.4.4b in a wild bird, in a single migratory brown skua (Stercorarius antarcticus). 

    This is the first detection of H5 HPAI in a wild bird Australia. 

    The virus is related to H5N1 HPAI clade 2.3.4.4b viruses detected in southern Indian Ocean territories. 

    The bird was displaying clinical signs of leg paralysis, weakness and dehydration at Cape Le Grand national park near Esperance, Western Australia. 

    Brown skuas are vagrant species that occasionally visit Australia. 

    There is no poultry production in the region. 

    Enhanced general and targeted surveillance is underway to determine the extent of infection. 

    An epidemiological investigation has commenced. 

    A public information strategy is being implemented. 

    All coordinates provided are approximate.

Source: 

Link: https://wahis.woah.org/#/in-review/7649

____

Lower limit of #detection of commercial respiratory virus RT – #PCR panels for #bovine #influenza #H5N1

 

Abstract

Objectives

The adaptation of clade 2.3.4.4b influenza A(H5N1) to dozens of mammalian species, including dairy cattle, raises concerns about potential spillover into humans. If the virus develops human-to-human transmissibility, sensitive diagnostics will be critical to containment efforts. We sought to determine the lower limit of detection of commercial influenza A tests for the circulating bovine-adapted strain of H5N1.

Methods

We determined the 95% lower limit of detection (LLOD) of 4 commercial respiratory virus panels for detecting inactivated bovine H5N1 (A/bovine/Ohio/B24OSU-439/2024). Two of the tested panels provide seasonal influenza A subtyping, the BioFire Respiratory Panel 2.1 (BioFire Diagnostics/BioMérieux) and the cobas eplex respiratory pathogen panel 2 (Roche Diagnostics), while 2 panels provide pan–influenza A detection, the Xpert Xpress CoV-2/Flu/RSV plus (Cepheid), and the Panther Fusion SARS-CoV-2/Flu A/B/RSV Assay (Hologic, Inc). Serial dilutions of H5 RNA (400-25 copies/mL) were prepared in respiratory virus–negative nasopharyngeal swab matrix, and 20 replicates were tested at each concentration. The 95% LLOD for each test was calculated using probit regression.

Results

All 4 tests detected H5 with 95% LLODs below 1000 H5 RNA copies/mL. Xpert demonstrated the highest analytical sensitivity (50 copies/mL; 95% CI, 39-160), followed by BioFire (297 copies/mL; 95% CI, 196-3955), Panther Fusion (531 copies/mL; 95% CI, 421-792), and eplex (883 copies/mL; 95% CI, 588-2741).

Conclusions

Existing commercial respiratory virus panels can effectively detect bovine H5N1. These platforms could support screening in the event of an H5N1 outbreak, followed by confirmation with specific H5 subtyping, as needed.

Source: 

Link: https://academic.oup.com/ajcp/article-abstract/165/6/aqag067/8709618?redirectedFrom=fulltext

____