ETIDIOH - NEW

  Abstract Background :  Genetic drift and host-associated adaptation in influenza A viruses threaten the long-term reliability of RT-qPCR-based diagnostics , particularly when nucleotide mismatches arise within primer and probe binding regions . Conventional assay evaluations often emphasize sequence conservation but rarely assess functional mismatch tolerance across divergent subtypes and hosts.  Methods :  We performed an in silico evaluation of a matrix (M) gene–targeted RT-qPCR assay by aligning primer and probe binding regions against 22 H1N1 isolates and representative H3N2 and H5N1 reference strains, including recent zoonotic isolates from avian and bovine hosts . Nucleotide mismatches were identified, quantified, and mapped relative to assay components and oligonucleotide termini. Mismatch burden was summarized by subtype and assay region.  Results :  H1N1 isolates exhibited complete conservation across primer and probe regions. In contrast, H3N2 a...

  ABSTRACT The recent emergence of highly pathogenic avian influenza (HPAI) H5N1 (clade 2.3.4.4b, genotype B3.13) in dairy cattle presents substantial challenges to the agricultural sector and public health. Mechanistic studies of infection and transmission in cattle have proven difficult due to animal handling restrictions and the limited availability of established cell culture models. Primary bovine embryonic fibroblasts (BeEFs) were isolated and investigated here as a model to study influenza A virus (IAV) infection dynamics. We compared sialylation profiles , infectious virus production, viral replication, and plaque morphology in BeEFs following infection with the bovine HPAI H5N1 and an earlier 2.3.4.4b genotype (B1.1) isolated in 2022. The data presented here demonstrate increased expression of α-2,3 sialic acids compared to α-2,6 sialic acids in BeEFs , similar to sialylation profiles previously reported in bovine mammary tissue . These data also display increased viral fi...

  Abstract The recent emergence of highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b in U.S. dairy cattle marks a pivotal shift in the ecology of influenza A viruses (IAVs), signaling an unexpected expansion into a major livestock species . This review explores the molecular mechanisms underpinning this cross-species transmission , focusing on the unique sialic acid receptor landscape of the bovine mammary gland as a critical determinant. We synthesize emerging evidence that this tissue, which co-expresses both avian-type (α2,3-linked) and human-type (α2,6-linked) sialic acid receptors , functions as a novel biological crucible for viral adaptation . Within this environment, H5N1 virus faces selective pressure for hemagglutinin (HA) mutations —such as Q226L and N193D—that can alter receptor binding specificity toward human-like glycans , potentially bridging the species barrier. Recent studies confirm that bovine H5N1 virus isolates exhibit dual receptor-binding avidity ...

  Abstract The spillover of highly pathogenic avian influenza (HPAI) A H5N1 virus to mammalian hosts raises major concerns due to its pandemic potential . Cats are frequently affected mammals, often succumbing to systemic and neurological disease . Here, we characterized the pathogenesis and transmissibility of two H5N1 genotypes, B3.13 and D1.1, in cats . Infected cats exhibited high-level viremia and virus shedding in nasal, oral, and fecal secretions were consistently detected. The virus replicated initially in the upper respiratory tract and lungs , followed by systemic dissemination and neuroinvasion . Notably, the virus crossed the blood-brain-barrier by infecting endothelial cells , spreading to astrocytes and neurons , causing multifocal encephalitis . D1.1-virus infection caused protracted disease with lower shedding and no transmissibility , whereas B3.13 virus caused rapid onset with efficient shedding and transmission. These findings reveal critical H5N1 neuropathogenes...

  {Excerpt} Time Period: February 08, 2026 - February 14, 2026 -- H5 Detection :  9 site(s) ( 1.9% ) -- No Detection :  466 site(s) ( 98.1% ) -- No samples in last week :  171 site(s) The H5 detections at sewershed IDs 809 and 912 in Michigan are false detections resulting from a data error. These will be corrected in the next update. (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  Poultry farms in Andhra Pradesh State. Source:  Link:  https://wahis.woah.org/#/in-review/7268 ____

{By Pkspks - Own work, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=162556362 } ___ More than 300 House Crows in Bihar: Darbhanga, Patna, Bhagalpur, Katihar, Pashchim Champaran Regions.  Source:  Link:  https://wahis.woah.org/#/in-review/7269 ____

  Abstract Intercontinental spread of highly pathogenic avian influenza A(H5N1) viruses poses significant pandemic risks and necessitates strong protective countermeasures . We evaluated the therapeutic efficacy of the neuraminidase inhibitor oseltamivir , the polymerase inhibitors baloxavir and favipiravir , and an ion-channel blocker amantadine , against severe influenza A( H5N1 ) virus infection in female BALB/c mice . Baloxavir (≥10 mg/kg, 1 dose) fully protected mice from death , significantly reduced virus respiratory replication, and prevented neuroinvasion . Oseltamivir (≥100 mg/kg/day for 5 days) provided limited survival benefits , reduced lung titers but failed to prevent viral neuroinvasion . Favipiravir (≥100 mg/kg/day for 5 days) provided partial protection , although did not reduce viral titers in lungs and brain . Amantadine provided no benefits . Although all drugs inhibited A(H5N1) viruses in vitro, in vivo correlations did not extend beyond baloxavir . Our result...

  Abstract B etween 2022 and 2025, highly pathogenic avian influenza viruses (HPAIVs) of clade 2.3.4.4b, including four distinct H5 Eurasian (EA) genotypes , were detected in wild birds and mammals in the Svalbard Archipelago and on the island of Jan Mayen . We describe their epidemiology and genomic characteristics to improve understanding of HPAIV occurrence and transmission in the High Arctic . The initial cases in 2022 occurred during summer and involved a glaucous gull (Larus hyperboreus) and great skuas (Stercorarius skua) on Svalbard and Jan Mayen , representing the first detections of HPAIVs in the High Arctic . Three HPAIV genotypes were identified: EA-2020-C (H5N1), EA-2021-AB (H5N1), and EA-2021-I ( H5N5 ). In 2023 , HPAIVs were detected in a broader range of bird species, and retrospectively in an Atlantic walrus reported by another research group (Odobenus rosmarus rosmarus). Genotypes identified in 2023 were EA-2020-C (H5N1), EA-2021-I ( H5N5 ), and EA-2022-BB (H5N1)....

  By Andrew Shiva / Wikipedia, CC BY-SA 4.0,  https://commons.wikimedia.org/w/index.php?curid=46772024 ___ Samples were taken from dead wild animals during a research voyage to Heard Island, an Australian sub-Antarctic external territory. HPAI was detected from samples taken from two gentoo penguins . This follows initial detections in southern elephant seals on an earlier voyage in October 2025. There was no further evidence of ongoing mass mortality detected during the second voyage in January 2026. Further sequencing and phylogenetic analysis is being undertaken. Source:  Link:  https://wahis.woah.org/#/in-review/7261 ____

  Backyard poultry in Chhukha Region. Source:  Link:  https://wahis.woah.org/#/in-review/7263 ____

  Abstract Despite Antarcticas geographic isolation, the first incursion of high pathogenicity avian influenza (HPAI) H5N1 was detected in the 2023/24 austral summer . Surveillance for HPAI H5N1 in Antarctica remains patchy due to logistical, financial, and infrastructure challenges , with many suspected cases remaining unconfirmed , and few viral genomes sequences available to date. Through the 2024/25 austral summer we undertook five sampling expeditions to the South Shetland Islands and Antarctic Peninsula facilitated by cruise ships/operators. Across more than 500 faecal environmental samples collected from apparently healthy penguins and marine mammals , we found no detectable evidence of HPAI H5N1 . However, HPAI H5N1 was detected in all but one of the skua carcasses sampled , which, in most cases, were found within meters of penguin sub-colonies . All HPAI H5N1 viral genomes sequences from skuas on the Antarctic Peninsula fell within a single lineage, which included those ge...

{Excerpt} Avian Influenza Report - Reporting period: February 8, 2026 – February 14, 2026 (Week 7)   (...) - Date of report: 14/02/2026 - Country: Cambodia - Province / Region: Kampot province - District / City: Tuek Chhou district - Sex: M - Age: 30 - Condition at time of reporting: Recovered - Subtype of virus: H5N1 (...) Source:  Link:  https://www.chp.gov.hk/files/pdf/2026_avian_influenza_report_vol22_wk07.pdf ____

  Backyard poultry in Zhemgang Region. Source:  Link:  https://wahis.woah.org/#/in-review/7262 ____

  {Excerpt} Time Period: February 01, 2026 - February 07, 2026 -- H5 Detection :  8 site(s) (1.7%) -- No Detection :  475 site(s) (98.3%) -- No samples in last week :  166 site(s) The H5 detections at sewershed IDs 809 and 912 in Michigan are false detections resulting from a data error. These will be corrected in the next update . (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  Abstract After rebounding from near extirpation during the organochlorine era, breeding Peregrine Falcons (Falco peregrinus) in California are again facing adversity, this time consistent with an outbreak of a highly pathogenic avian influenza . Following the first detection of the H5N1 variant clade 2.3.4.4b virus in California wild birds in July 2022, we assembled data from long-term monitoring (2000-2025) of peregrine breeding territory occupancy in the broad vicinity of San Francisco Bay to examine possible impacts on falcon populations. Prior to the outbreak, 47 focal breeding territories had shown nearly complete occupancy by pairs (98.5% of 390 site-years), with very few vacancies, single birds in attendance, or subadult pair members. Within 8 mo of the outbreak, occupancy had dropped to 65.1%, and 2 yrs later (2025), only 36.2% of sites remained occupied . An uptick in site-occupancy by single birds also occurred after the outbreak, but it is unclear whether these were su...

  Abstract Clade 2.3.4.4b highly pathogenic avian influenza A(H5N1) viruses continue to expand geographically and across mammalian hosts, raising concern about pandemic potential. The degree and specificity of pre-existing immunity in humans are key determinants of this risk. We analyzed hemagglutinin (HA)- and neuraminidase (NA)-specific antibody responses in 300 sera collected from adults in New York City. While HA directed binding antibodies to clade 2.3.4.4b H5 were low and hemagglutination-inhibiting antibodies were absent, we detected widespread binding and functional NA antibodies against N1 neuraminidases from clade 2.3.4.4b H5N1 viruses. Neuraminidase inhibition (NI) titers were highest against North American D1.1 genotype N1 viruses and correlated strongly with neutralizing activity, whereas HA-binding antibodies did not. An additional N-linked glycosylation site, as found in the NA of a human D1.1 isolate from British Columbia, reduced susceptibility to NI antibodies. An...

  A slaughter turkeys operation in Dolnośląskie Region. Source:  Link:  https://wahis.woah.org/#/in-review/7258 ____

  Abstract The outbreak of Highly Pathogenic Avian Influenza H5N1 in U.S. dairy cattle poses substantial risks to public health, economic sustainability of farming, and global food systems . Using a Computable General Equilibrium model , we simulate its short- to medium-term impacts on Gross Domestic Product and other macro-economic outcomes for the US and its main trading partners . We simulate impacts under the current situation and realistic and reasonable worst-case scenarios . We estimate domestic economic losses ranging between 0.06% and 0.9% of US GDP , with losses to the dairy sector ranging between 3.4% and 20.6%. Trading partners increase dairy production to compensate for the loss. Current government subsidies are about 1.2% (95% HDI: 1% to 1.4%) of output losses, and likely insufficient to incentivise farmers to step up surveillance and biosecurity for mitigating the possible emergence of H5N1 strains with pandemic potential into human populations. Source:  Link:...

  Abstract The polymerase acidic (PA) protein is a subunit of the trimeric influenza A virus (IAV) RNA-dependent RNA polymerase and the target of the anti-influenza drug baloxavir marboxil (BXM). As with other direct-acting antivirals , treatment with BXM can lead to selection of viruses carrying resistance mutations . If these mutations have negligible fitness costs, resistant viruses can spread widely and render existing treatments obsolete . Multiple BXM resistance mutations in the nuclease domain of PA have been identified, with I38T and I38M amino acid substitutions occurring frequently. These mutations have minimal to no effects on viral polymerase activity , virus replication , or transmission . However, for reasons that are not well understood, viruses with BXM resistance substitutions have not been able to compete with parental wild-type strains . The IAV genome segment encoding PA also encodes the host shutoff nuclease PA-X, which shares the endonuclease domain with PA bu...