Avian #influenza #overview June–August 2026 (ECDC/EFSA, September 22 '26, Summary)

 

{Summary}

Abstract

    Between 5 June and 28 August 2026, 110 highly pathogenic avian  influenza (HPAI) A(H5N1) virus detections were reported in domestic (7)  and wild (103) birds in 12 countries in Europe. The number of detections  remained at a seasonal low throughout the summer, continuing the decline  observed since spring. In contrast to previous years, fewer colony-breeding  seabirds were affected, and the geographical range of detections was more  limited. Further sporadic detections of HPAI A(H5) virus were reported in wild  terrestrial carnivores and pinnipeds. Outside Europe, the epidemic continued  in the Americas, where also the HPAI A(H7N3) subtype was detected in Mexico.  Following its first introduction to mainland Australia, HPAI A(H5N1) virus spread within local wild bird populations and spilled over to terrestrial  carnivores and marine mammals. In the US, the number of dairy  cattle farms reportedly affected by HPAI A(H5N1) increased, while detections in  captive American minks were reported for the first time. Between 5 June and  31 August 2026, 15 cases of avian influenza virus infection were publicly  reported in humans (no fatal cases) in three countries and territories:  Bangladesh (one A(H5N1) case), Cambodia (one A(H5N1) case) and China (13 A(H9N2) cases). All 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.

©2026 European Food Safety Authority, European Centre for Disease Prevention  and Control, European Union Reference Laboratory for Avian Influenza. EFSA  Journal published by WileyVCH GmbH on behalf of European Food Safety Authority

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Source: 

Link: https://doi.org/10.2903/j.efsa.2026

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#Mexico - #Influenza A #H7N3 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

{Click on Image to Enlarge}

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By Chuck Homler d/b/a FocusOnwWildlife - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=150451071

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    ° As a result of efforts to promote reporting, an outbreak of HPAI H7N3 was detected in a wild bird in the State of Chiapas. 

    ° Active epidemiological surveillance continues nationwide in commercial poultry farms, backyard flocks, and slaughterhouses, as well as monitoring of wild birds.

    ° A wild bird {a Plain chachalaca} that was not part of the zoo's collection, found in the vicinity of the zoo.

Source: 

Link: https://wahis.woah.org/#/in-review/7716

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#Genomic similarity to quantitatively evaluate the #reassortment #potential of #H7N9 with other subtypes of avian #influenza viruses

 

Abstract

Introduction: 

The H7N9 influenza virus poses a significant public health threat due to its potential for reassortment and cross-species transmission. This study aims to systematically evaluate the genomic similarity between H7N9 and other influenza A subtypes to identify strains with high reassortment potential and characterize their spatiotemporal and host distribution patterns.

Methods: 

We analyzed nearly 4,000 H7N9 sequences from GISAID and NCBI, alongside representative sequences of other influenza A subtypes. Open reading frames were extracted, and a genomic similarity index was constructed using Euclidean distance, dot product, and cosine similarity measures, with weights optimized via principal component analysis. The index was applied to quantify inter-subtype similarity and predict reassortment-prone strains.

Results: 

High sequence similarity was observed between H7N9 and cognate subtypes (e.g., H7N3, H15N9), with H7N3 exhibiting the highest similarity index (1.00). Validation using known reassortant strains, such as A/Yixing/805/2022 (H3N2), confirmed that strains with high reassortment potential showed significantly elevated similarity scores across all gene segments (p< 0.001). High-similarity outliers analysis identified 581 spillover events, temporally concentrated during 2014–2017, and spatially clustered in regions like the United States, Europe, and Hong Kong. Host analysis highlighted birds—especially chickens, ducks, and turkeys—as key reservoirs for reassortment.

Discussion: 

The genomic similarity index effectively identifies influenza A subtypes with high reassortment potential, supported by retrospective validation and spatiotemporal congruence with documented outbreaks. The concentration of high-similarity strains in specific hosts and regions underscores the role of ecological factors in viral evolution. These findings provide a predictive framework for monitoring emergent reassortants and inform targeted surveillance strategies.

Source: 

Link: https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2026.1777911/full

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#Ecology of low pathogenicity avian #influenza virus #H7 in wild #birds in south-eastern #Australia prior to emergence of high pathogenicity avian influenza H7 in #poultry

 

Abstract

Adding to the global burden of high pathogenicity avian influenza (HPAI) H5N1, an unprecedented five HPAI H7 outbreaks occurred globally in 2024. Of these, three occurred in southeast Australia, with the independent emergence of HPAI H7N9, H7N8, and H7N3, resulting in the destruction of 2 million poultry. Historical data demonstrates that H7 outbreaks in Australia do not occur randomly, rather, there is a strong association between the timing of the previous H7 outbreaks and rainfall patterns in southeastern Australia. We aimed to address a hypothesis wherein prior to H7 outbreaks in poultry, there was a detectable change in H7 prevalence and/or virus diversity in wild bird populations. We addressed this using virological and serological surveillance data generated from multiple programs. Despite the collection of thousands of samples, there was only weak evidence to support our hypothesis, which provides strong incentive to evaluate current surveillance approaches for the purposes of risk prediction. However, in alignment with a previous analysis, there is strong support for a relationship between H7 outbreak probability and rainfall patterns across southeast Australia. Overall, improved understanding of the ecology and evolution of H5 and H7 viruses in wild bird reservoirs is pivotal to global disease preparedness and response.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Australian Department of Agriculture Fisheries and Forestry

Australian Department for Health and Aged Care

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.08.693062v1

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#Genetic and Serological Analysis of #H7N3 Avian #Influenza Viruses in #Mexico for #Pandemic #Risk Assessment

 

Abstract

Avian influenza A viruses pose ongoing threats to human and animal health, with H7 subtypes causing outbreaks globally. In Mexico, highly pathogenic H7N3 viruses have circulated in poultry since 2012, causing sporadic human infections. Here we analyzed genetic markers in hemagglutinin sequences from Mexican H7N3 isolates and conducted serological assays on human populations with poultry exposure. Our results show conserved avian-like receptor binding sites, thus limiting human adaptation, alongside antigenic drift and acquisition of glycosylation sites likely driven by vaccination. Serological testing of 1103 individuals revealed no detectable antibodies against H7N3, indicating a naïve population. Phylogenetic analyses revealed multiple virus clades circulating regionally. These findings suggest that while current H7N3 viruses have limited capacity for sustained human transmission, the lack of population immunity underscores the importance of continued surveillance and risk assessment to mitigate potential pandemic threats.

Source: Viruses, https://www.mdpi.com/1999-4915/17/10/1376

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