#India - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

 

A poultry farm in the Maharashtra State.

Source: 

Link: https://wahis.woah.org/#/in-review/7469

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

 

Backyard poultry in Kiev Region.

Source: 

Link: https://wahis.woah.org/#/in-review/7495

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Emergence of D1.1 #reassortant #H5N1 avian #influenza viruses in North #America

 

Abstract

Since 2021, highly pathogenic avian influenza viruses (HPAIVs) belonging to H5N1 clade 2.3.4.4b have circulated widely in North American wild birds and repeatedly spilled over into mammals. In 2025, the first H5N1-associated deaths in humans were recorded in the Western hemisphere, raising questions about how the ongoing evolution of the virus in wild birds impacts spillover risk. Here, our analysis of 21,471 H5N1 genomes identified an evolutionary shift in mid-2024, driven by interhemispheric migration from Asia and reassortment with new antigens. The genotypes that dominated the early years of North America's H5N1 epizootic traced their ancestry back to Europe, but Asia was the source of new "D1.1" genotype viruses that (a) spread faster, (b) have higher reassortment potential, (c) a broader host range, (d) repeatedly spill over to bovines, and (e) cause severe disease in humans, including non-farm workers.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Research Foundation - Flanders, https://ror.org/03qtxy027, G098321N, G0E1420N

European Union Horizon 2023 RIA project LEAPS, 101094685

DURABLE EU4Health project 02/2023-01/2027, 101102733

Fonds National de la Recherche Scientifique, F.4515.22

European Union Horizon 2020 project MOOD, 874850

Centers of Excellence for Influenza Research and Response, National Institute of Allergy and Infectious Diseases, National Institutes of Health (NIH), Department of Health and Human Services, 75N93021C00014

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.19.695329v2

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#Poland - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

 

A poultry farm in the Lubelskie Region.

Source: 

Link: https://wahis.woah.org/#/in-review/7451

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#India - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

 

A poultry farm in the Chhattisgarh Region.

Source: 

Link: https://wahis.woah.org/#/in-review/7453

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#Chile - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

 

A poultry farm in Araucanía Region.

Source: 

Link: https://wahis.woah.org/#/in-review/7456

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#UK, #England - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

{England, Lincoln Region} A commercial flock of 3,800 laying ducks. Samples taken were positive for HPAI H5N1. Birds presented clinical signs prior to testing.

Source: 

Link: https://wahis.woah.org/#/in-review/7440

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#IvoryCoast - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

 

A poultry farm in Zanzan Region.

Source: 

Link: https://wahis.woah.org/#/in-review/7446

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Respirable #Aerosol #Production and Reduction of Avian #Influenza #Transmission #Risk during #Chicken Processing, #Bangladesh

 

Abstract

In Bangladesh, influenza A(H5N1) viruses are endemic in poultry. Processing infected chickens can aerosolize viruses, increasing the risk for human infections. We evaluated particulate matter (PM2.5) mass concentration during slaughtering and defeathering methods used in live bird markets in Bangladesh to identify solutions to reduce aerosol exposure. We slaughtered 675 chickens using cones and barrels with 3 lid types and defeathered 45 chickens using a defeathering machine with 5 lid types. We interviewed 3 slaughterers to understand method preference. For slaughtering, barrels with a solid or star-cut lid reduced PM2.5 mass concentrations by 65%–73% compared with uncovered barrels. For defeathering, machines fully covered by a solid lid or lid with a hole and pivot door reduced PM2.5 mass concentrations by 50% compared with machines with no lid. Slaughterers preferred barrels covered with solid lids and defeathering machines covered with solid or hinged lids. Those methods might reduce aerosol exposure during poultry processing.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/32/4/25-1878_article

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

All [Backyard] birds at the site were culled; surveillance measures continue in the control zone. [Region: Libertador General Bernardo O'Higgins]

Source: 

Link: https://wahis.woah.org/#/in-review/7400

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#Genetic and #biological characterization of a #duck-origin clade 2.3.4.4b #H5N6 avian #influenza virus reveals partial #mammalian #adaptation

 

Highlights

• Duck-origin H5N6 virus A/Duck/Jiangsu/628/2022 shares high homology with the human strain A/Yangzhou/125/2022.

• The 628 strain shows mammalian adaptation markers: HA mutations enhance human receptors affinity and NA mutations reduce sensitivity to neuraminidase inhibitors.

• Limited airborne transmission but detectable droplet-mediated spread suggests increased mammalian transmission risk.

Abstract

Clade 2.3.4.4b H5Nx highly pathogenic avian influenza viruses (HPAIVs) have caused extensive outbreaks in poultry worldwide. H5 HPAIVs have caused sporadic but severe human infections in China, representing a persistent zoonotic threat. Here, we identified a duck-origin H5N6 HPAIV (A/Duck/Jiangsu/628/2022) through routine surveillance and assessed its biological characteristics and mammalian pathogenesis. Phylogenetic analysis revealed > 98% nucleotide identity between strain 628 and the concurrent human H5N6 strain A/Yangzhou/125/2022. Molecular characterization identified multiple mammalian adaptation markers: hemagglutinin substitutions (S137A, T160A, T192I) associated with enhanced human receptor binding; neuraminidase mutations (I117T, D198N) linked to reduced neuraminidase inhibitor susceptibility; and polymerase complex changes (PB1-D622G, PA-K142Q) conferring increased mammalian cell replication. In vitro studies demonstrated that 628 virus replicated more efficiently in mammalian than in avian cells and exhibited dual receptor-binding specificity. Mouse pathogenicity assays revealed moderate virulence with progressive lung pathology. Critically, transmission experiments confirmed both direct contact and airborne transmission capabilities of 628 in guinea pigs. These findings demonstrate that circulating H5N6 viruses have acquired partial mammalian adaptation while retaining avian fitness, significantly elevating pandemic potential. Enhanced surveillance of wild bird populations, poultry farms, and live poultry markets is urgently needed to develop effective prevention and control strategies.

Source: 

Link: https://www.sciencedirect.com/science/article/abs/pii/S037811352600146X?via%3Dihub

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#Surveillance and cross-species #transmission #assessment of #H3NX avian #influenza viruses isolated in #Guangdong province, #China from 2023 to 2025

 

Abstract

Continued influenza surveillance remains important, especially given that the emergence of novel subtypes or reassorted influenza viruses with pandemic potential continues to be a worldwide threat. In particular, virus circulating in birds can facilitate interspecies transmission to humans. In this study, we conducted systematic surveillance of H3 subtype avian influenza virus (AIVs) in domestic poultry and wild birds throughout Guangdong Province from 2023 to 2025. A total of 21 strains of H3 subtype AIVs were isolated, and phylogenetic analyses and risk assessment of their internal gene segments revealed genetic evidence of reassortment events, indicating a close genetic relationship with highly pathogenic avian influenza viruses (HPAIVs). ZJ1722, ZJ1542 and SZ837 showed dual-receptor binding ability and robust replication in mammalian cells, which coincided with amino acid mutations in the HA protein associated with human receptor binding. Although the H3NX viruses isolated in this study failed to cause lethality in mice, they efficiently replicated in the nasal turbinate and lungs of mice without prior adaptation. This study highlights the paramount importance of sustained, subtype-specific surveillance targeting H3NX avian influenza viruses coupled with timely risk characterization and assessment. Proactive containment of H3NX avian influenza virus (AIV) transmission has vital implications for safeguarding the sustainability of the poultry industry and protecting global human public health, given the inherent zoonotic potential and evolutionary plasticity of this H3 subtype, which could drive future spillover events.

Source: 

Link: https://www.sciencedirect.com/science/article/pii/S0032579126004918?via%3Dihub

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#Serological #Surveillance of Avian #Influenza Virus #H9N2 Subtype in #Occupational Populations Exposed to #Poultry Environment in #China During 2018–2023

 

Abstract

Background

Avian influenza virus (AIV) H9N2 has a major role in the emergence of influenza pandemic. We assessed the risk of AIV H9N2 to the human population and public health.

Method

The hemagglutination inhibition method was used to screen for hemagglutinin antibodies. Microneutralization tests were performed to confirm neutralizing antibodies against the AIV H9N2 subtype. Real-time polymerase chain reaction was conducted to detect the H9 subtype in environmental samples. GraphPad Prism software was used for mapping, and STATA software was used for statistical analysis.

Results

The nationwide seroprevalence among these populations was 0.76%. Seroprevalence was compared across regions, genders, and occupational exposure sites. The seroprevalence rates for males and females showed no significant difference. Significant differences were found across regions and occupational exposure environments (P < .05). The south and southwest regions had the highest seroprevalence rates at 1.58% and 1.38%, respectively. The highest seroprevalence was observed in individuals exposed to live poultry market (1.51%). Significant regional differences in H9 nucleic acid positive rates (NAPRs) were found (P < .05), with the southwest and central regions showing the highest rates at 25.99% and 24.35%, respectively. H9 NAPR in live poultry markets (LPMs), farms, and slaughterhouses varied significantly by region (P < .05).

Conclusions

Poultry-related environments have become a key factor in AIV H9N2 infection among occupational populations. Exposure to LPM showed the highest seroprevalence among occupational groups. The distribution characteristics of H9N2 across different poultry environments increased the risk of infection in occupationally exposed populations.

Source: 

Link: https://academic.oup.com/ofid/article/13/4/ofag144/8537381

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#Chile - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

 

This incident is occurring in the Maule Region, in the municipality of San Rafael, on a recreational property where two owners are responsible for the total number of birds reported. All of the birds will be humanely culled, and the carcasses will be buried on the property under strict biosecurity measures.

Source: 

Link: https://wahis.woah.org/#/in-review/7405

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#Cambodia - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds & one #human case) (2017-) - Immediate notification

 

On 26 March 2026, an outbreak investigation team visited a backyard farm following reports of illness and mortality suspected to be caused by Avian Influenza (AI). A total of five samples (three chickens and two ducks) were collected and submitted to NAHPRI/GDAHP for testing of Avian Influenza (H5N1). On 27 March 2026, laboratory results confirmed that three out of five samples (two chickens and one duck) tested positive for Avian Influenza (H5N1). Additionally, in the same area, one human case of Avian Influenza (H5N1) was confirmed by the Ministry of Health on 31 March 2026.

Source: 

Link: https://wahis.woah.org/#/in-review/7409

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Deciphering #HPAI #Influenza A Virus #H5N1: Molecular Basis of #Pathogenicity, Zoonotic Potential, and Advances in #Vaccination Strategies

 

Abstract

The ongoing panzootic of the highly pathogenic avian influenza (HPAI) H5N1 virus, dominated by clade 2.3.4.4b, constitutes a significant global threat to wildlife, animal health, and public health. Once characterized by sporadic outbreaks, H5N1 has evolved into a sustained, year-round infection with an expanded host range that now includes numerous mammalian species. Its high pathogenicity is primarily driven by the acquisition of a polybasic haemagglutinin cleavage site, enabling systemic viral spread, alongside emerging endothelial and neurotropic properties that contribute to severe disease and high mortality in mammals. Although zoonotic transmission remains limited, H5N1 continues to accumulate mutations associated with mammalian adaptation, particularly within the haemagglutinin and polymerase complex. Notably, recent outbreaks in U.S. dairy cattle highlight the emergence of novel mammalian reservoirs with increased human exposure risk. Concurrently, vaccination strategies are advancing beyond traditional adjuvanted inactivated vaccines toward next-generation platforms, including mRNA and virus-like particle vaccines, designed for rapid deployment and broader immune protection. However, ongoing viral evolution, constrained vaccine availability, and gaps in coordinated surveillance underscore the urgent need for an integrated One Health approach to reduce panzootic risk.

Source: 

Link: https://www.mdpi.com/1999-4915/18/4/410

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#Nepal - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

Frequent sightings of wild birds were reported in the vicinity of the farm. The farm comprises multiple poultry sheds having birds of different age (4-56 weeks) groups. On 15 March, a sudden mortality event occurred in one shed, where approximately 100 commercial layer birds died acutely. Since that incident, mortality has been observed across all sheds on the farm.

Commercial Layers of various age (4-56 weeks) group affected since 15 March, 2026 and a large number of chicken appear slightly droopy or depressed, and die suddenly.

Source: 

Link: https://wahis.woah.org/#/in-review/7386

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

{Bântéay Méanchey, Preah Netr Preah} On 12 March 2026, the outbreak investigation team visited a backyard chicken farm following reports of illness and mortality suspected to be caused by Avian Influenza (AI). During the visit, deaths of wild birds were also observed in the area. A total of six chicken samples were collected and submitted to NAHPRI/GDAHP for testing of Avian Influenza (H5N1). Laboratory results confirmed on 16 March 2026 that 4 out of 6 chicken samples tested positive for Avian Influenza (H5N1). In addition, 13 wild bird carcasses were collected and submitted for laboratory testing. On 16 March 2026, all wild bird samples were confirmed positive for Avian Influenza (H5N1).

{Bântéay Méanchey, Serei Saophoan} On 25 January 2026, the outbreak investigation team visited a backyard chicken farm following reports of illness and mortality suspected to be caused by Avian Influenza (AI). Two chicken samples were collected and submitted to NAHPRI/GDAHP for testing of AI (H5N1). On 26 January 2026, laboratory results confirmed that both samples tested positive for Avian Influenza (H5N1).

Source: 

Link: https://wahis.woah.org/#/in-review/7376

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#Peru - #Influenza A #H5 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

In the framework of passive surveillance activities, a report was received regarding backyard poultry (not considered as poultry) with clinical symptoms consistent with avian influenza. An outbreak of high pathogenicity avian influenza has been confirmed in the Cajabamba district of the Cajamarca department. The birds showed clinical signs such as weakening, hoarseness, eye discharge, and diarrhoea. The Official Authority activated quarantine, control, and surveillance measures in the outbreak and around the outbreak with the aim of identifying possible cases and preventing the spread of the outbreak.

A notification was received regarding sick birds in a backyard (turkeys, ducks, roosters, hens, geese, and chickens) showing signs of depression, diarrhoea, and hoarseness.

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

Link: https://wahis.woah.org/#/in-review/7358

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#UK - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

 

{Northern Ireland}

Pheasant breeder flock, with a small mixed backyard flock with chicken, geese. Positive test for HPAI H5N1, clinical signs presented prior to testing.

Source: 

Link: https://wahis.woah.org/#/in-review/7368

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