ETIDIOH - NEW

  Abstract Zoonotic spillover of influenza A viruses into humans has repeatedly triggered pandemics throughout history. Since their emergence in the 1990s, H5N1 influenza viruses have significantly expanded their geographical range and host species , raising global concern about the potential for sustained human-to-human transmission . In this review , we examine the virological characteristics of currently circulating H5N1 strains, key molecular barriers limiting their spread among humans, and critical areas of future research to mitigate the ongoing H5N1 panzootic and prevent future pandemics. Source:  Link:  https://academic.oup.com/immunohorizons/article/9/SI/vlaf062/8381786 ____

  Abstract In the austral summer 2023/2024, H5N1 high pathogenicity avian influenza virus (HPAIV) was reported for the first time in Antarctica . Concerns of HPAIV causing high mortality of seabirds and mammals prompted immediate efforts to track its spread and impact on endemic wildlife. In March 2024, we visited the Danger Islands archipelago , that hosts two mega-colonies of Adélie penguins , and observed an unusual mortality estimated in thousands of Adélie penguins and other species . Swabs and tissues were collected for molecular detection of infectious agents from 49 carcasses, and additional tissues for histology from a selection of 9 carcasses. We unexpectedly detected Pasteurella multocida DNA in 46 of 49 individuals, and diagnosed avian cholera , and not HPAI , as the cause of death of most of these animals. By metagenomics, we retrieved the genomic sequences of the Pasteurella multocida strain which caused the epizootic, and the phylogenetic analysis showed a close rela...

  A mute swan in Mazowieckie Region. Source:  Link:  https://wahis.woah.org/#/in-review/7123 ____

Samples from Qieding District, Kaohsiung City and Annan District, Tainan City were sent to the National Laboratory, Veterinary Research Institute (VRI), for diagnosis. Highly pathogenic avian influenza H5N1 subtype were confirmed by VRI. The sampling spots were disinfected. Surrounding poultry farms within 3 km radius of the sampling spot are under intensified surveillance for 28 days. By Cp9asngf - Own work, CC BY-SA 3.0,  https://commons.wikimedia.org/w/index.php?curid=27358997 A dead black-faced spoonbill (Platalea minor) was found in Sicao, Annan District, Tainan City. The specimen was sent to National Reference Laboratory for testing. It was confirmed as Highly Pathogenic Avian Influenza (HPAI) on December 7. ___ By Photo by Laitche, CC BY-SA 4.0,  https://commons.wikimedia.org/w/index.php?curid=46904763 A dead Eurasian Wigeon (Anas penelope) was found in Qieding District, Kaohsiung City. The specimen was sent to National Reference Laboratory for testing. It was confirmed...

A wild Greylag Goose in Podlaskie Region. Source:  Link:  https://wahis.woah.org/#/in-review/7096 ____

  By MPF - Own work, CC BY-SA 4.0,  https://commons.wikimedia.org/w/index.php?curid=102468449 Approximately 30 wild birds on an island near Lüderitz were observed exhibiting clinical signs consistent with highly pathogenic avian influenza (HPAI). Enhanced and continuous surveillance activities are ongoing to assess the extent of infection and monitor potential spread. Source:  Link:  https://wahis.woah.org/#/in-review/7120 ____

  Abstract Avian influenza H5N1 clade 2.3.4.4b viruses caused a global panzootic and, unexpectedly, widespread outbreaks in dairy cattle , therefore representing a pandemic threat . To inform control strategies, it is critical to determine whether the potential to adapt to bovine cells is a general feature of H5N1 viruses , is specific to viruses of clade 2.3.4.4b, or narrowly restricted to some genotypes within this clade. Using a large panel of recombinant viruses representing >60 years of H5N1 history and other IAVs for comparison, we demonstrate replicative fitness in bovine cells is: (i) highly variable across 2.3.4.4b genotypes, (ii) limited in viruses predating the global expansion of this clade , (iii) determined by the internal gene cassette, and (iv) not restricted to udder epithelial cells. Mutations in the PB2 polymerase subunit emerge as key determinants of adaptation , although their phenotypic effects are context dependent. Bovine B3.13 and some avian genotypes ex...

  Abstract The highly pathogenic avian influenza H5N1 virus clade 2.3.4.4b has been spreading globally since 2022 , causing mortality and morbidity in domestic and wild birds, as well as in mammals , which underscores its potential to cause a pandemic . Here, we generate a panel of anti-hemagglutinin (HA) human monoclonal antibodies (mAbs) against the H5 protein of clade 2.3.4.4b. To develop human chimeric antibodies , H2L2 Harbor Mice®, which express human immunoglobulin germline genes, were immunized with H5 and N1 recombinant proteins from A/mallard/New York/22-008760-007- original/2022 H5N1 virus. Through hybridoma technology, sixteen fully human mAbs are generated, most of which show cross-reactivity against H5 proteins from different clade 2.3.4.4 virus variants . Fourteen out of the sixteen mAbs neutralize the virus in vitro . The mAbs with the strongest hemagglutination inhibition activity also demonstrate greater neutralizing capacity and show increased protective effects ...

  Abstract Genomic sequencing of reemerging highly pathogenic avian influenza A(H5N1) virus detected in Argentina in February 2025 revealed novel triple-reassortant viruses containing gene segments from Eurasian H5N1 and low pathogenicity viruses from South and North American lineages . Our findings highlight continued evolution and diversification of clade 2.3.4.4b H5N1 in the Americas. Source:  Link:  https://wwwnc.cdc.gov/eid/article/31/12/25-0783_article ____

  {Excerpt} Time Period: November 30, 2025 - December 06, 2025 -- H5 Detection :  2 site(s) ( 0.5% ) -- No Detection :  390 site(s) ( 99.5% ) -- No samples in last week :  54 site(s) (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  Abstract In autumn 2025, an unprecedented mass mortality event was observed among the western migrating subpopulation of Eurasian cranes (Grus grus) in Germany . Systemic infection with highly pathogenic avian influenza virus H5N1 , clade 2.3.4.4b, genotype DI.2.1, was identified as the cause of acute death. The gregarious behavior of cranes at feeding and resting sites likely has contributed to the rapid and massive dissemination of viruses within the crane population. Competing Interest Statement The authors have declared no competing interest. Funder Information Declared European Union, 101084171 Source:  Link:  https://www.biorxiv.org/content/10.64898/2025.12.08.692485v1 ____

  The outbreak affecting captive birds was in an establishment with 4 laying hens , 1 cock and 1 runner duck located in Harju county, Viimsi parish . The outbreak was confirmed on the 9th of December 2025 based on analysis performed tracheal and brain samples at the National Centre for Laboratory Research and Risk Assessment, and in accordance with the case definition. Measures were only applied in the outbreak establishment. Based on a risk assessment, no restricted zone was established around the affected establishment in accordance with Article 21(3)(g). The establishment concerned kept only 6 captive birds and they had no direct or indirect contact with poultry or other establishments keeping captive birds . In the establishment, all captive birds were already dead. No culling was necessary. Preliminary cleaning and disinfection was applied. Source:  Link:  https://wahis.woah.org/#/in-review/7092 ____

  Abstract Highly pathogenic avian influenza H5N1 rarely infects mammals. In 2024-2025, however, genotypes B3.13 and D1.1 caused two independent spillovers into U.S. dairy cattle . By analysing 26,930 complete H5N1 genomes from global surveillance , we identified 73 major viral groups , most of which show continent-specific distribution in Europe, Asia, Africa , and North America . North American viruses exhibit higher genetic diversity in specific viral segments , including variants potentially associated with mammalian adaptation . Both dairy-cattle-associated B3.13 and D1.1 genotypes originate from the same geographic macro-area , suggesting a possible regional hotspot where avian-mammalian interfaces may facilitate viral adaptation. Our findings place the U.S. outbreaks in a global framework and indicate that North American H5N1 may be predisposed to cross-species transmission. Competing Interest Statement The authors have declared no competing interest. Funder Information Decl...

  Abstract Efficient replication of influenza A viruses (IAVs) requires balanced activities of hemagglutinin (HA), neuraminidase (NA), and the RNA polymerase complex, whose functions are strongly influenced by PB2 mutations . We previously revealed three distinct evolutionary pathways for PB2 mutations, with two pathways leading to the emergence of viral strains responsible for human seasonal infections and the 2009 pandemic , and a third pathway giving rise to H5Nx highly pathogenic avian influenza viruses (HPAIVs) defined by a triad of mutations (I147T, K339T, and A588T) that occasionally spill over to humans . Here, we investigated the zoonotic risk posed by this triad and elucidated its evolutionary relationship with HA, NA, and vaccination . Recombinant PR8 and clade 2.3.2.1c H5N1 viruses carrying the triad replicated efficiently in embryonated chicken eggs and had moderate replication efficiency in mammalian cells ; moreover, mice infected with these viral strains exhibited m...

  {England, Kent} Laying flock with around 31K birds. Samples taken were positive for HPAI H5N1. Birds presented clinical signs prior to testing. {England, Suffolk} Backyard flock. Samples taken were positive for HPAI H5N1. Birds presented clinical signs of AI prior to testing. Source:  Link:  https://wahis.woah.org/#/in-review/7081 ____

  Abstract The unprecedented 2.3.4.4b. A(H5N1) outbreak in dairy cattle, poultry, and spillover to humans in the United States (US) poses a major public health threat. Population immunity is a critical component of influenza pandemic risk assessment . We assessed the pre-existing cross-reactive immunity to 2.3.4.4b A(H5N1) viruses and analyzed 1794 sera from 723 people (0.5–88 yrs) in multiple US geographic regions during 2021–2024. Pre-existing neutralizing and hemagglutinin (HA)-head- binding antibodies to A(H5N1) were low , but there were substantial cross-reactive binding antibodies to N1 neuraminidase (NA) of 2.3.4.4b A(H5N1). Antibodies to group 1 HA stalk were also prevalent and increased with age . A(H1N1)pdm09 infection and influenza vaccination did not induce neutralizing antibodies to A(H5N1) viruses but induced significant rise of functional NA inhibition (NAI) antibodies to N1 of 2.3.4.4b A(H5N1), and group 1 HA stalk antibodies . Moreover, pre-pandemic stockpiled 2.3....

  Abstract Influenza remains a significant global public health concern. Live-attenuated influenza vaccines (LAIVs) are recognized as effective interventions for influenza prevention. Currently, two types of LAIVs are licensed for human use: one developed through cold-adapted viral gene mutation and the other through the deletion of the viral NS1 gene . However, the similarities and differences in these two LAIVs’ efficacy, safety, and immune responses have not been thoroughly studied. This study constructed a gene-deficient live-attenuated vaccine strain, CA4-dNS1, and a gene locus-mutated attenuated vaccine strain, CA4-cold , to compare their in vivo and in vitro replication capacity , broad-spectrum protective efficacy , safety, and immunogenicity . The results showed that both LAIVs provide comparable broad-spectrum protection against lethal H1N1 and H5N1 influenza challenges in mice and induce similar humoral and mucosal immune responses . Notably, the CA4-cold vaccine strain ...

{Excerpt} Country 2024 (cases - deaths) - 2025 (cases - deaths) - Total (cases - deaths) 1) Australia - 1 - 0 - 0 - 0 - 1 - 0   2) Azerbaijan - ... - ... - 0 - 0 - 8 - 5  3) Bangladesh - ... - ... -  3 - 0 - 11 - 1  4) Cambodia - 10 - 2 - 17 - 8 - 89 - 51  5) Canada - 1 - 0 - 0 - 0 - 2 - 1  6) Chile - ... - ... - 0 - 0 - 1 - 0  7) China - 1 - 0 - 1 - 0 - 57 - 32  8) Djibouti - ... - ... - 0 - 0 - 1 - 0  9) Ecuador - ... - ... - 0 - 0 - 1 - 0  10) Egypt - ... - ... - 0 - 0 - 359 - 120  11) India - ... - ... - 2 - 2 - 3 - 3  12) Indonesia - ... - ... - 0 - 0 - 200 - 168  13) Iraq - ... - ... - 0 - 0 - 3 - 2  14) Lao People's Democratic Republic - ... - ... - 0 - 0 - 3 - 2  15) Mexico - ... - ... - 1 - 1 - 1 - 1  16) Myanmar - ... - ... - 0 - 0 - 1 - 0  17) Nepal - ... - ... - 0 - 0 - 1 - 1  18) Nigeria - ... - ... - 0 - 0 - 1 - 1  19) Pakistan - ... - ... - 0 - 0 - 3 - 1  20) Spain - ... - ...

  Abstract Finland faced an outbreak of highly pathogenic clade 2.3.4.4b A(H5N1) avian influenza in 2023, which spread from wild birds to fur farms . Vaccinations of at-risk individuals began in June 2024 using the MF59-adjuvanted inactivated A(H5N8) vaccine (Seqirus; A/Astrakhan/3212/2020, clade 2.3.4.4b). Here, in an observational study , we assessed vaccine-induced immune responses in occupational at-risk individuals participating in the phase IV trial , including virus-specific antibody (n = 39 individuals) and T-cell (n = 18 individuals) responses. Vaccination elicited functional antibodies against the vaccine virus and two heterologous clade 2.3.4.4b strains associated with outbreaks on Finnish fur farms and dairy cattle in the United States . Among previously unvaccinated individuals, seroprotection rates against the vaccine virus were 83% (95% CI 70–97%) by microneutralization assay (titre ≥20) and 97% (90–100%) by haemagglutination inhibition assay (titre ≥40). In those pr...

  Abstract Increase in human H5N1 spillover infections resulting from dissemination of highly pathogenic avian influenza (HPAI) virus into bird and mammal populations raises concerns about HPAI gaining human transmissibility . Studies identified hemagglutinin (HA) acid stability and receptor preference as essential traits that shape host tropism. Mutations that increase HA stability and affinity for α−2,6-linked sialic acids have been shown to confer airborne transmissibility in a ferret model , however mechanisms of activation of H5 subtype HA are poorly understood and the effect of adaptive mutations on HA function has been largely inferred from static structures. Here, we use hydrogen/deuterium-exchange mass spectrometry to dissect activation dynamics for two ancestral H5 HPAI HA , their transmission-adapted HA , and a contemporary HA . We identify variation in receptor binding site flexibility and demonstrate that adaptive mutations result in suppression of fusion peptide dynam...