ETIDIOH - NEW

  Abstract Avian influenza viruses (AIVs), including H5N1 and H7N9, from the Orthomyxoviridae family present substantial public health concerns . The predominant circulating clade 2.3.4.4b has demonstrated enhanced capacity for mammalian adaptation , raising concerns about potential reassortment with human seasonal influenza viruses . Unlike H7N9 ’s limited host range , H5N1 infects birds, various mammals, and humans . Recent concerns include widespread H5N1 infection of U.S. dairy cattle across 18 states , affecting over 1000 herds with 71 human infections (70 H5N1 and 1 H5N5). Key observations include cow-to-cow transmission, viral presence in milk, and transmission to humans , mainly through occupational exposure . Evidence of mammal-to-mammal transmission has been documented in European and Canadian foxes and South American marine mammals . Standard pasteurization effectively inactivates the virus in milk. The continuing mammalian adaptations , particularly mutations like PB2-E...

  {Excerpt} Time Period: December 14, 2025 - December 20, 2025 -- H5 Detection :  1 site(s) ( 0.2% ) -- No Detection :  461 site(s) ( 99.8% ) -- No samples in last week :  57 site(s) (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  Abstract Avian influenza is a global public health threat. Since 2021, the ongoing H5N1 panzootic has brought a major shift in H5Nx epidemiology , including unprecedented spread, wide host range and lack of seasonality . Infections in marine mammals, wildlife and livestock have heightened concern for human-to-human transmission and pandemic potential . Contact tracing and self-isolation are used as public health measures in the UK to manage contacts of confirmed human cases of avian influenza. In this study, we aimed to estimate potential outbreak sizes and evaluate the effectiveness of contact tracing and self-isolation in managing community outbreaks of H5N1 following spillover from birds to people . We characterised contact patterns from an underrepresented agricultural population at high risk of avian influenza exposure through contact with birds (Avian Contact Study). Informed by these realistic social contact data, we modelled outbreak sizes using a stochastic branching pro...

  Abstract Highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b has recently emerged as a major threat to wildlife , agriculture, and public health due to its expanding host range and the increasing frequency of spillover into mammals . In July–August 2023, the mass death of over 3500 northern fur seals (Callorhinus ursinus) and at least one Steller sea lion (Eumetopias jubatus) was recorded on Tyuleniy Island in the Sea of Okhotsk, Russia. Two HPAI A( H5N1 ) viruses were isolated from fur seal carcasses and designated A/Northern_fur_seal/Russia_Tyuleniy/74/2023 and A/Northern_fur_seal/Russia_Tyuleniy/75/2023. Both viruses exhibited high pathogenicity in chickens (IVPI 2.7–3.0) and mice (MLD50 1.9–2.5 log10EID50/mL), with distinct differences in disease progression, histopathology, and organ tropism . Experimental infection of mice revealed that strain A/74/2023 induced more severe pulmonary and neurological lesions than A/75/2023. Whole-genome sequencing and phylogeneti...

  Abstract Human (avian) influenza A viruses, especially highly pathogenic avian influenza (HPAI) viruses, pose a significant public health threat , and a multivalent vaccine is the primary prophylactic measure to control these viruses. To establish such a vaccine, we generated two multivalent vesicular stomatitis virus (VSV)-based vaccine candidates (V-EtM2e/H505 and V-EtM2e/H522) and characterized their ability to induce protective immune responses. Our results revealed that vaccine immunization in mice induced high humoral immune responses against both the HPAI hemagglutinin (HA) protein and the ectodomain of M2 (M2e) protein . Intriguingly, vaccine-immunized mouse sera exhibited highly efficient neutralizing activity against the corresponding H5 pseudovirus and mediated potent and broad antibody-dependent cellular cytotoxicity (ADCC) activity against M2e derived from human and avian influenza H5, H1, H3, and H7 viruses . Furthermore, both intranasal and intramuscular immunizati...

  Abstract The global spread of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b viruses has recently extended to include diverse mammalian species , raising new concerns about pandemic risk . In 2023, this clade was first detected in Russian marine mammals during a mass mortality event among northern fur seals in the Far East . Genetic analyses revealed the causative viruses to belong to genotype A3 of European origin , which is known to have circulated in wild birds across the Far East since 2022. Notably, these isolates harbor the mammalian-adaptive substitutions PB2-K482R and NP-N319K—mutations previously linked to enhanced virulence in non-H5 avian influenza viruses , but whose impact on A(H5N1) clade 2.3.4.4b viruses remained to be characterized. The heightened virulence of A3 genotype viruses is confirmed by data obtained via a mouse model . However, despite these adaptive changes, ferret transmission models showed no evidence of airborne transmission of the fur seal...

  The Official Veterinary Service (OVS) of the state of Mato Grosso received a notification of a suspected case influenza A viruses of high pathogenicity in domestic birds from a multi-species backyard , on December 20, 2025. Official Laboratory (LFDA-SP) analysis confirmed the presence of the H5N1 virus, clade 2.3.4.4b. The premises have been placed under quarantine. Birds will be culled, and carcasses, products, and any potentially contaminated materials will be destroyed. The OVS is currently conducting an epidemiological investigation in the surrounding area. Source:  Link:  https://wahis.woah.org/#/in-review/7147 ____

  Abstract Since 2021, highly pathogenic avian influenza viruses (HPAIV) belonging to H5N1 clade 2.3.4.4b have caused high mortality in North American wild birds and poultry . In 2025 , a new D1.1 genotype caused two human deaths and host-switched to dairy cattle . However, the evolutionary origins and dynamics of D1.1 have not been fully characterized. Here, our phylogenetic analysis of 17,516 H5N1 genome sequences uncovers how D1.1 introduced a major shift in the antigenic diversity and ecology of the H5N1 epizootic in North America. D1.1 is the first major H5N1 genotype to (a) emerge in the Pacific flyway and spread west-to-east faster than any prior genotype; (b) antigenically shift via reassortment with the North American N1 segment, displacing the previously fixed Eurasian N1 ; and (c) transmit to a broader range of host species than any H5N1 genotype to date, introducing mammalian adaptations . Competing Interest Statement The authors have declared no competing interest. Fun...

  Abstract Poultry workers in Washington, USA, were infected with highly pathogenic avian influenza A(H5N1) virus and recovered. The viruses were clade 2.3.4.4b genotype D1.1, closely related to viruses causing poultry outbreaks . Continued surveillance and testing for influenza A(H5) clade 2.3.4.4b viruses remain essential for risk assessment and pandemic preparedness of zoonotic influenza viruses. Source:  Link:  https://wwwnc.cdc.gov/eid/article/31/12/25-1118_article ____

  Abstract Many pathogens, both those with human spillover potential as well as avian-specific viruses, are maintained in wild bird populations . While much surveillance for influenza A viruses (IAVs) is performed annually, surveillance for other pathogens is limited. Sampling of wild birds is often time-consuming , labour-intensive, involves physically handling wild birds, often limited in sample size, and involves handling of potentially infected birds , posing an increased risk of direct exposure for personnel. Given this, additional methods for surveillance are needed. Longitudinal, bi-weekly fecal and sediment sampling was performed at various sites in southern Manitoba, Canada , particularly focused in Winnipeg from May - October 2025. Sites were chosen based on the suitability of the area for waterfowl habitat , the presence of waterfowl in the area, as well as sites in proximity to reported outbreaks of H5N1 influenza virus . Fecal and sediment samples were collected and sc...

  Influenza at the human-animal interface  Summary and risk assessment, from 6 November to 19 December 2025 {1} -- New human cases {1,2}:  - From 6 November to 19 December 2025, based on reporting date , the detection of influenza A( H5N1 ) in one human , A( H5N5 ) in one human , A( H9N2 ) in seven humans , and an influenza A( H1N1 ) variant virus in one human were reported officially.  - In addition , one human case of infection with an influenza A( H1N2 ) variant virus was detected.  -- Circulation of influenza viruses with zoonotic potential in animals :  - High pathogenicity avian influenza (HPAI) events in poultry and non-poultry animal species continue to be reported to the World Organisation for Animal Health (WOAH).{3}  - The Food and Agriculture Organization of the United Nations (FAO) also provides a global update on avian influenza viruses with pandemic potential.{4}  - Additionally, low pathogenicity avian influenza viruses as well a...

  ~155K laying chickens’ flock. Samples taken were positive for HPAI H5N1. Birds presented clinical signs prior to testing. Source:  Link:  https://wahis.woah.org/#/in-review/7139 ____

  Abstract Highly pathogenic avian influenza H5N1 poses an increasing public health risk, particularly following its spillover into dairy cows and associated human infections in the U.S. since March 2024. Here, we systematically identified critical PB2 mutations emerged during avian-to-cattle transmission and subsequent adaptation in cattle , notably PB2 M631L, which conferred pathogenicity in mice comparable to the well-characterized PB2 E627K mutation . Retrospective analysis reveals that PB2 631L also circulated in avian and human H5N1 strains during the 2013–2014 outbreaks in Cambodia and Vietnam . Additional adaptive mutations include established markers ( E627K, Q591R, D701N ), and novel variants ( I647V, G685R, K736R ). These mutations enhance polymerase activity by improving the utilization of both bovine and human ANP32A proteins , thereby increasing viral fitness and pathogenicity in mammals . The convergence of these adaptations highlights the elevated zoonotic risk of c...

  Abstract Avian influenza virus (AIV) infections in cats are a new and not fully understood  problem  in Poland . These infections have drawn the attention of both veterinarians  and human medical  practitioners , mainly because of their zoonotic  potential , i.e. possible spreading to humans and  other mammals . In wild felids as  well as in domestic cats , AIV can cause severe infections , often  ending in death.  Highly pathogenic avian influenza virus (HPAIV) and low pathogenic avian  influenza virus (LPAIV) have been identified, with the recent H5N1 (2.3.4.4b  clade) outbreak  affecting poultry, wild birds and carnivores .  Transmission likely occurs through contact with  infected birds , their excretions or  contaminated raw poultry , while cat-to-cat transmission  remains unconfirmed .  First reported in Thailand in 2003, H5N1 infections in cats have since  occurred in  multiple c...

  WASHINGTON, D.C., December 19, 2025 On December 14, 2025, USDA’s Animal and Plant Health Inspection Service (APHIS) announced the first detection of highly pathogenic avian influenza (HPAI) in a dairy herd in Wisconsin .  On December 17 , the National Veterinary Services Laboratories (NVSL) completed whole genome sequencing and confirmed that the virus is H5N1 clade 2.3.4.4b genotype D1.1.  Analysis indicates that this detection is a new spillover event from wildlife into dairy cattle, separate from previous events. Key Points -- Most detections in U.S. dairy herds have resulted from movements linked to the original spillover event that occurred in the Texas Panhandle in late 2023, involving the B3.13 strain . -- In early 2025, through the National Milk Testing Strategy , USDA detected two spillover events in Nevada and Arizona dairy herds. Both were identified early, and no further herd infections occurred through animal movements. These events involved the D1.1 strain...

  Abstract Highly Pathogenic Avian Influenza (HPAI) viruses, particularly IAV (H5N1), continue to pose a major global threat due to their widespread circulation and high mortality rates in birds. Management of HPAI is complicated by challenges in conserving migratory bird populations, sustaining poultry production, and uncertainties in disease dynamics. Structured decision-making frameworks , such as those based on the PrOACT model, are recommended to improve outbreak response and guide critical actions , especially when HPAI virus (HPAIV) detections occur in sensitive areas like wildlife refuges . Surveillance data from late 2024 to early 2025 show persistent HPAI activity , with 743 detections across 22 European countries and beyond, and notable outbreaks in poultry in nations like Hungary, Iceland, and the UK . The proximity of poultry farms to water sources increases environmental contamination risks. Meanwhile, HPAI A(IAV (H5N1)) and other H5Nx viruses have been detected in a ...

  {Excerpt} Time Period: December 07, 2025 - December 13, 2025 {*} -- H5 Detection :   3 site(s) ( 0.7% ) -- No Detection :  451 site(s) ( 99.3% ) -- No samples in last week :  37 site(s) {*} Note: The H5 detection at site 2030 in Virginia is a result of a data error and is a false detection. This will be corrected in the next update. (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____