ETIDIOH - NEW

  Abstract High pathogenicity avian influenza virus (HPAIV) H5N1 reached the sub-Antarctic and Antarctica in 2023 , subsequently spreading to remote locations within this region where it had devastating impacts on seal, penguin and albatross populations . The threat to marine wildlife over this broad area exemplifies the need to understand H5N1 long-distance dispersal and evolution . We obtained 104 novel viral genomic sequences from samples that we collected at South Georgia, Kerguelen, Crozet, Prince Edward, Falklands/Malvinas Islands and the Antarctic Peninsula in a region spanning 8,000 kilometers . Using recent phylogeographic modeling advances we show that H5N1 spread encompassed numerous transmission events between distant locations, accumulating mammalian-adaptive mutations in the process. Seals are the most affected species, but we reveal that the long-distance eastward virus dispersal better aligns with the long-distance movements of large petrels and albatrosses . The ri...

Weekly epidemiological record   20 MARCH 2026, 101th YEAR, No 12, 2026, 101, 53–56 http://www.who.int/wer   Executive Summary   The WHO Expert Working Group on Surveillance of Influenza Antiviral Susceptibility (AVWG) supports the WHO GISRS by providing practical guidance for monitoring antiviral susceptibility of seasonal and emerging influenza viruses through global surveillance efforts .  The 14th WHO-AVWG meeting was held in virtual format on 10-12 June 2025 .  Update on susceptibility of seasonal influenza viruses to approved antiviral agents   From approximately May 2024 to May 2025 , five WHO Collaborating Centres (CCs) and two National Influenza Centres (NICs) reported co-circulation of influenza A(H1N1) pdm09, A(H3N2), and B/Victoria viruses.  A(H1N1)pdm09 dominated in Eastern Asia {1}. Elevated frequency of influenza neuraminidase (NA) inhibitor (NAI) reduced inhibition/ highly reduced inhibition (RI/HRI) was identified among A(H1N1)pdm09 vir...

  {Excerpt} Time Period: March 08, 2026 - March 14, 2026 -- H5 Detection :  8 site(s) ( 1.8% ) -- No Detection :  444 site(s) ( 98.2% ) -- No samples in last week :  120 site(s) (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  By USFWS Mountain-Prairie - Canada goose on Seedskadee NWR, Public Domain,  https://commons.wikimedia.org/w/index.php?curid=69188087 ___ A wild Canada Goose in Etelä-Suomen aluehallintovirasto Region. Source:  Link:  https://wahis.woah.org/#/in-review/7384 ____

  Abstract The ongoing epizootic of highly pathogenic avian influenza (HPAI) continues to cause massive deaths in wildlife . Fundamental understanding of its disease ecology in natural populations is urgently needed. This knowledge has been hindered by the difficulty of acquiring data on epidemic dynamics . Here, using data collected from a threatened population of Dalmatian pelicans (Pelecanus crispus), we recover the epidemiological and evolutionary history of one of the largest HPAI wildlife mortality events . The results show that this devastating outbreak was likely seeded by a single introduction associated with movement of the species . By estimating epidemiological features of two consecutive outbreaks in the same population, we show that panzootic H5N1 since 2022 likely exhibits higher transmissibility and longer shedding time in non-reservoir birds , compared to previous H5NX subtypes. We also evaluate effectiveness of past and future control measures : carcass removal du...

{Bântéay Méanchey, Preah Netr Preah }  On 12 March 2026, the outbreak investigation team visited a backyard chicken farm following reports of illness and mortality suspected to be caused by Avian Influenza (AI). During the visit, deaths of wild birds were also observed in the area. A total of six chicken samples were collected and submitted to NAHPRI/GDAHP for testing of Avian Influenza (H5N1). Laboratory results confirmed on 16 March 2026 that 4 out of 6 chicken samples tested positive for Avian Influenza (H5N1 ). In addition, 13 wild bird carcasses were collected and submitted for laboratory testing. On 16 March 2026, all wild bird samples were confirmed positive for Avian Influenza (H5N1). {Bântéay Méanchey, Serei Saophoan}  On 25 January 2026 , the outbreak investigation team visited a backyard chicken farm following reports of illness and mortality suspected to be caused by Avian Influenza (AI). Two chicken samples were collected and submitted to NAHPRI/GDAHP for tes...

{Excerpts} Avian Influenza Report - VOLUME 22, NUMBER 11 - Reporting period: March 8, 2026 – March 14, 2026 (Week 11) (Published on March 17, 2026)   (...) -- Date of report :  14/03/2026 -- Country :  Cambodia -- Province / Region District / City :  Banteay Meanchey province, Preah Netr, Preah district -- Sex :  Female -- Age :  45 -- Condition at time of reporting :  Hospitalised -- Subtype of virus : H5N1   (...) Source:  Link:  https://www.chp.gov.hk/files/pdf/2026_avian_influenza_report_vol22_wk11.pdf ____

  {Automatic translation, edited} Kingdom of Cambodia -  Press Release A Case of Bird Flu in a 45-year-old Woman The Ministry of Health of the Kingdom of Cambodia would like to inform the public that there is 1 case of bird flu in a 45-year-old woman who was confirmed to be positive for the H5N1 avian influenza virus on March 14, 2026 by the National Institute of Public Health. The patient resides in Ropai village, Chinu Meanchey commune, Preah Net Preah district, Banteay Meanchey province , and there were reports of sick and dead chickens in the village .  On the same day, the patient was placed in isolation at the hospital and was treated with Tamiflu and received careful care from the medical team.  Upon inquiry, it was revealed that the patient raised chickens and ducks , including some sick and dead chickens. 3 days before testing positive, she had come into contact with the dead chicken. The National and Sub-National Health Ministry's Emergency Response Team ha...

  Abstract The ongoing outbreak of highly pathogenic avian influenza virus (HPAIV) subtype H5N1 in the U.S. poses a significant public health threat . To date, 70 human cases have been confirmed in the United States , including two severe cases and one fatality . While suitable animal models are crucial for predicting the potential pandemic risk of newly emerging pathogens in humans, studies investigating contemporary HPAIV H5N1 transmission dynamics remain limited. Here, we investigate the pathogenicity and transmission efficiency of recent clade 2.3.4.4b H5N1 viruses isolated from a bovine, mountain lion, and a human case using Syrian hamsters . Intranasal inoculation results in productive virus replication in the respiratory tract and shedding for all three isolates . Transmission studies demonstrate limited efficiency via direct contact and airborne routes for all isolates. Although overall transmission is inefficient , the human H5N1 isolate demonstrates relatively greater con...

{Excerpt} Time Period: March 01, 2026 - March 07, 2026 -- H5 Detection :  8 site(s) ( 1.6% ) -- No Detection :  491 site(s) ( 98.4% ) -- No samples in last week :  77 site(s) (...) Source: US Centers for Disease Control and Prevention,  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  In the framework of passive surveillance activities, a report was received regarding backyard poultry (not considered as poultry) with clinical symptoms consistent with avian influenza. An outbreak of high pathogenicity avian influenza has been confirmed in the Cajabamba district of the Cajamarca department . The birds showed clinical signs such as weakening, hoarseness, eye discharge, and diarrhoea. The Official Authority activated quarantine, control, and surveillance measures in the outbreak and around the outbreak with the aim of identifying possible cases and preventing the spread of the outbreak. A notification was received regarding sick birds in a backyard (turkeys, ducks, roosters, hens, geese, and chickens) showing signs of depression, diarrhoea, and hoarseness. Source: WOAH,  https://wahis.woah.org/#/home Link:  https://wahis.woah.org/#/in-review/7358 ____

  {Northern Ireland} Pheasant breeder flock, with a small mixed backyard flock with chicken, geese. Positive test for HPAI H5N1, clinical signs presented prior to testing. Source:  Link:  https://wahis.woah.org/#/in-review/7368 ____

  Abstract We investigated the evolutionary history of the newly emergent neuraminidase (am4N1) associated with the D1.1 and D1.2 genotypes of highly pathogenic avian influenza A(H5N1) viruses in North America . Phylogenetic inference places am4N1 in a sister clade to Eurasian avian, swine, and human A(H1N1)pdm09 viruses and distinct from 1918, pre-2009 human seasonal, and classical swine A(H1N1) lineages . Am4N1 descends from diverse avian N1 genes endemic to the Americas. Phylodynamic analysis indicates a monophyletic am4N1 lineage with numerous introductions of viruses carrying the am4N1 gene likely originating from western Canada into the United States during emergence of the D1.1 and D1.2 genotypes. The lineage has diversified and accumulated deletions in the stalk domain . Despite amino acid divergence, structural modeling shows conserved neuraminidase architecture in the globular head . Given its distinct ancestry and amino acid sequence, further studies are needed to assess...

{Valparaíso} The birds shared a pond with wild birds. All birds were culled and buried on the property under strict biosecurity protocols. Cleaning and disinfection measures are being carried out. Source:  Link:  https://wahis.woah.org/#/in-review/7357 ____

  Abstract Highly pathogenic influenza A viruses of the H5 subtype continue to diversify worldwide through mutation and genetic reassortment , generating novel variants with unpredictable consequences under the One Health approach . Between 2024 and 2025 , five outbreaks of avian influenza A viruses were detected in backyard poultry across Michoacán, Estado de México , and Ciudad de México . We conducted molecular and genetic characterization of five highly pathogenic H5N2 viruses isolated from these events. All cases tested positive for influenza A virus and the H5 hemagglutinin , exhibiting high pathogenicity with intravenous pathogenicity index values ranging from 2.88 to 3.0. Whole-genome sequencing revealed novel reassortants containing hemagglutinin from Eurasian H5N1 clade 2.3.4.4b and neuraminidase from the endemic Mexican H5N2 lineage . The viral genome of the isolate from Michoacán contained six segments derived from Eurasian H5N1 viruses introduced into North America in ...

  Within the epidemiological surveillance carried out by the Colombian Agricultural Institute aimed at the early detection of clinical signs consistent with avian influenza, an outbreak of high pathogenicity avian influenza (HPAI) was confirmed in the village of Porvenir, in the municipality of Puerto Concordia in the department of Meta . The event concerns non-poultry in a backyard , for which respiratory and neurological signs were observed. The National Veterinary Authority activated epidemiological tracing and epidemiological monitoring 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. Source:  Link:  https://wahis.woah.org/#/in-review/7345 ____

  Abstract Background :  The emergence of the highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b in North America , beginning in February 2022, has highlighted the dynamic, unpredictable, and regionally variable risk of infections . Studies are needed to assess the spatiotemporal clustering of HPAI H5 at the interface between wild waterfowl and commercial poultry to understand and mitigate this risk .  Methods :  Publicly available data on HPAI H5 detections in wild birds and commercial poultry from January 2022 to January 2026 were analyzed at the county level. Retrospective space-time permutation models were used to identify and scan for clusters with higher than expected detection rates.  Results :  A total of 17,091 HPAI H5 detections were reported in wild birds across 1,467 county-level locations. Four species , Mallard ( Anas platyrhynchos ) (2,848 detections, 16.66%), Canada goose ( Branta canadensis ) (1,496, 8.75%), Green-winged teal ( An...

  Abstract A human infection with clade 2.3.4.4b H5N1 influenza A virus in Canada revealed minority variants E190D and Q226H in the hemagglutinin (HA) receptor-binding site (RBS). Because mutations at positions 190 and 226 have been associated with altered receptor specificity in other influenza subtypes, we investigated their impact on receptor binding in H5 HA . Using a recombinant protein approach and an ELISA-based glycan-binding assay , we assessed binding to representative avian- and human-type sialylated glycans . Both single mutations and their combination resulted in a complete loss of detectable binding to the tested glycans . To evaluate whether this phenotype was background-dependent, Q226H was additionally introduced into two other H5 HA proteins , each representing a distinct clade . In both cases, the mutation similarly abolished receptor binding . These findings independently validate recent glycan microarray observations and demonstrate that the patient-derived E19...

  Abstract Highly pathogenic avian influenza (HPAI) viruses of H5N1 clade 2.3.4.4b, are spreading worldwide , posing a threat to wildlife, domestic animals, and humans . In 2025, a multidisciplinary collaboration for HPAI H5N1 surveillance among birds within Galveston County, Texas , was initiated. Between November and December 2025, oropharyngeal and cloacal swabs were collected from wild and domestic birds reported as dead or dying by Galveston County residents . Specimens were studied with molecular assays, Sanger sequencing, virus isolation, and next-generation sequencing. Molecular evidence of HPAI H5N1 was detected in 7 of 10 (70%) birds, and the virus was successfully cultured in MDCK cells . Next-generation sequencing analysis of eight influenza A genome segments demonstrated a 4:4 gene segment reassortant constellation within clade 2.3.4.4b, consistent with genotype D1.1. Community members exposed to HPAI were offered antiviral prophylaxis . No human infections were identi...

  Abstract Since 2020, H5Nx high pathogenicity avian influenza viruses (HPAIVs) have caused widespread disruptions not only to global agriculture and trade but also to the health of free-ranging wildlife . Pinnipeds have experienced greater mortality from H5Nx HPAIV than any other mammalian taxa . Emergent virus strains, persisting over long time periods and vast geographic distances , have repeatedly triggered large-scale mortality events in pinniped populations. Of particular concern is the spread of H5Nx HPAIV to the Southern Hemisphere —including the emergence of a marine mammal-adapted clade in South America and detections in the sub-Antarctic and Antarctic —and to other remote locations such as the Hawaiian Islands . These developments elevate concern for the world’s endangered, isolated and endemic pinnipeds . While managing HPAIV in any animal population is a formidable task, working with free-ranging marine mammals poses unique challenges. In this review and perspective pi...