ETIDIOH - NEW

  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...

  {Summary} Time Period: November 23, 2025 - November 29, 2025 -- H5 Detection :  2 site(s) ( 0.6% ) -- No Detection :  352 site(s) ( 99.4% ) -- No samples in last week :  102 site(s) (...) Source:   Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  A backyard, multi-species, farming operation was tested and confirmed positive for HPAI H5N1. Source:  Link:  https://wahis.woah.org/#/in-review/7072 ____

  Highlights •  Fermentation of raw milk for 7 h at 42 °C to pH 4.4 reduced AIV levelsAIV by ≤ 4.1 log10 EID50. •  Incubation of raw milk for 7 h at 42 °C to pH 6.6 reduced levels by ≤ 4.3 log10 EID50. •  PH, temperature and/or bacterial degradation appreciably reduced AIV levels in raw milk. Abstract In March 2024, highly pathogenic avian influenza (HPAIV) H5N1 was first detected in U.S. dairy cattle and has since spread to herds across at least 17 states. Infected cows typically present with mastitis, decreased milk production, and poor milk quality with high viral loads in milk . While commercial pasteurization of milk effectively inactivates avian influenza virus (AIV), growing consumer interest in raw milk and derived products raises public health concerns due to the risk of zoonotic transmission . Standard yogurt production includes an initial heating step at 82 °C for 30 min to denature milk proteins which also inactivates AIV . However, some home yogurt recip...

  Abstract The spillover of H5N1 clade 2.3.4.4b into dairy cattle has raised concerns over the safety of fluid milk . While no foodborne infection has been reported in humans, this strain has infected at least 70 people and milk from infected cows is known to be infectious by ingestion in multiple other species. Investigation into the public health threat of this outbreak is warranted. This farm-to-table quantitative microbial risk assessment (QMRA) uses stochastic models to assess the risk of human infection from consumption of raw and pasteurized fluid cow's milk from the United States supply chains. These models were parameterized with literature emerging from this outbreak, then employed to estimate the H5N1 infection risk and evaluate multiple potential interventions aimed at reducing this risk. The median (5th, 95th percentiles) probabilities of infection per 240-mL serving of pasteurized, farmstore-purchased raw, or retail-purchased raw milk were 7.66E-19 (2.39E-20, 4.02E-17...

  {Excerpt} To the Editor : In March 2024, public health agencies in the United States reported highly pathogenic avian influenza (HPAI) virus of subtype A( H5N1 ) in dairy cattle , with virus detected in milk samples from symptomatic animals. Viral genetic fragments were subsequently found in pasteurized retail dairy products , which aroused concern about potential exposure through the human food supply . Heat treatment has been shown to reduce or eliminate infectious virus from both milk from infected cows and milk spiked with HPAI A(H5N1) virus. However, whether HPAI A(H5N1) virus in spiked milk from healthy cows replicates the properties of virus in milk from infected cows is unclear. We directly compared the stability of HPAI A(H5N1) virus in infected cows’ milk with that in spiked milk at 4°C (refrigeration temperature) and after heat treatment at 63°C (low-temperature, longer-duration pasteurization) or 72°C (high-temperature, shorter-duration pasteurization). (...) (...) So...

{Excerpt} Several cats in Neuruppin have been infected with avian influenza , according to the Ostprignitz-Ruppin district administration . They have been taken into the care of the Office for Consumer Protection and Agriculture, the district announced. A cat infected with the H5N1 strain of the avian influenza virus was found dead in a wooded area near the town. Several media outlets have reported on this.  (...) Source:  Link:  https://www.tagesspiegel.de/berlin/vogelgrippe-in-brandenburg-katzen-mit-geflugelpest-infiziert--warnung-vom-kreis-15014940.html ____

  Fattening birds suddenly dead. No biosecurity measures or vaccination plan. San Marcos Region. Source:  Link:  https://wahis.woah.org/#/in-review/7064 ____

  Within the epidemiological surveillance carried out by the Colombian Agricultural Institute (ICA) aimed at the early detection of clinical signs consistent with avian influenza, an outbreak of Highly Pathogenic Avian Influenza (HPAI) was confirmed in the village of Las Mercedes , in the municipality of Guaranda , in the department of Sucre . The event concerns non-poultry in a backyard , where respiratory and neurological signs were observed. The National Veterinary System activated epidemiological tracing and follow-up actions in the area of origin of the affected birds. As a control measure, the stamping out of the birds in the epidemiological unit was carried out and, as a complementary measure, epidemiological surveillance was strengthened in the surrounding area to identify other possible cases and prevent the spread of the disease. The affected population is composed of birds in a backyard not considered to be poultry which tested positive for Highly Pathogenic Avian Influe...