ETIDIOH - NEW

  {Excerpt} Time Period: January 04, 2026 - January 10, 2026 -- H5 Detection :  8 site(s) ( 1.5% ) -- No Detection :  541 site(s) ( 98.5% ) -- No samples in last week :  66 site(s) (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  Abstract Influenza A viruses exhibit broad host tropism, infecting multiple species including humans, avian species, and swine. Swine influenza virus (SIV), while primarily circulating in porcine populations , demonstrates zoonotic potential with sporadic human infections . In this investigation, we identified two H1N1 subtype swine influenza A virus strains designated A/swine/China/SD6591/2019(H1N1) (abbreviated SD6591) and A/swine/China/SD6592/2019(H1N1) (abbreviated SD6592) in Shandong Province , China. The GenBank accession numbers of the SD6591 viral gene segments are PV464931-PV464938, and the GenBank accession numbers corresponding to each of the eight SD6592 viral gene segments are PV464939-PV464946. Phylogenetic and recombination analyses suggest potential evolutionary differences between the isolates. SD6591 displayed a unique triple-reassortant genotype : comparative nucleotide homology assessments demonstrated that the PB2, PB1, NP, NA, HA, and NEP genes shared the hi...

  {Excerpt} Time Period: December 28, 2025 - January 03, 2026 -- H5 Detection :  3 site(s) ( 0.7% ) -- No Detection :  428 site(s) ( 99.3% ) -- No samples in last week :  111 site(s) (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  ABSTRACT Current U.S. surveillance for highly pathogenic avian influenza A(H5N1) in humans prioritizes individuals with known animal exposures , potentially missing community-acquired infections . To address this gap, we implemented universal H5 subtyping of all influenza A-positive respiratory samples collected within our hospital system , regardless of patient exposure history. Between August 2024 and April 2025, we subtyped 4,488 influenza A-positive samples and identified two cases positive for H5 RNA in Alameda County, California, USA . The first case was a 14-month-old girl with mild respiratory symptoms and no H5N1 exposure risks ; sequencing of the sample revealed an H5 gene closely related to clade 2.3.4.4b, genotype B3.13 viruses circulating in U.S. dairies . The second case was a 79-year-old male, also with no known exposures , whose sample reproducibly tested positive with a high cycle threshold value but could not be confirmed by public health laboratories. Both pati...

  {Excerpt} Time Period: December 21, 2025 - December 27, 2025 -- H5 Detection :  4 site(s) ( 1.1% ) -- No Detection :  359 site(s) (98.9%) -- No samples in last week :  168 site(s) (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____

  Abstract Highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b has expanded rapidly across the Southern Ocean since 2023 , causing extensive mortality in sub-Antarctic wildlife . Yet its penetration into Antarctica and impacts on ice-dependent species remain poorly resolved primarily due to surveillance constraints . We report the first confirmed H5N1 infection in an Antarctic ice-dependent seal (crabeater seal; Lobodon carcinophaga) and document mortality of crabeater seals across the northern Weddell Sea during November-December 2024 . Combining genomic, serological and observational data across nine species, we detected H5N1 RNA in a crabeater seal and a kelp gull (Larus dominicanus), and recovered complete HA, NA and M2 gene sequences from both. Phylogenetic analyses allowed us to identify at least two independent introductions of HPAI H5N1 clade 2.3.4.4b into the northern Antarctic Peninsula region. Serology provided strong evidence of prior exposure in scavenging bir...

  {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 Mexico has experienced recurrent viral epidemics of substantial intensity, including hyperendemic dengue, COVID-19, and recent reports of avian influenza A (H5N1) infections in birds , which pose an ongoing risk of zoonotic transmission . Mexico was also the location for the earliest detection of the pdmH1N1 virus during the 2009 influenza A pandemic. Under a One Health framework , markets represent a unique opportunity for low-cost virus monitoring at the human-animal interface . Under the hypothesis that these represent sentinel sites for an early virus detection , we implemented a pilot surveillance program at the central market of Merida city, Yucatan , Mexico, considered a regional hotspot for multiple and recent viral outbreaks . Longitudinal sampling was carried out over 11 months at 1-to-6-week intervals from April 2022 to February 2023 . We used multi-type surveillance in mosquitoes, live poultry, and wastewater . All samples were screened using RT-qPCR . Positi...

{Excerpt}  Avian influenza A(H9N2) :  -- Guangdong Province :  1) An individual with onset in November 2025.  -- Guangxi Zhuang Autonomous Region :  2) An individual with onset in November 2025.  -- Hubei Province:  3) An individual with onset in November 2025.  (...) Source:  Link:  https://www.chp.gov.hk/files/pdf/2025_avian_influenza_report_vol21_wk51.pdf ____

  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...

  Abstract We characterized influenza A(H1N1)pdm09, A(H3N2), and B/Victoria viruses circulating in Japan during 2023–2024 , focusing on lineage placement relative to WHO-recommended vaccine strains and on baloxavir resistance (PA/I38T substitutions). We enrolled 210 outpatients with influenza-like illness across eight clinics in six prefectures (October 2023–September 2024). Of these, 209 had an analyzable pre-treatment respiratory specimen for RT-PCR; hemagglutinin (HA) and neuraminidase (NA) genes were sequenced by next-generation sequencing (NGS). PA/I38T substitutions that confer baloxavir resistance were assessed by cycling-probe RT-PCR, Sanger sequencing, and NGS. HA phylogenies were constructed with global datasets and WHO vaccine reference strains. Of 209 pre-treatment specimens, 181 were influenza-positive (A(H1N1)pdm09 44.2%, A(H3N2) 37.6%, B/Victoria 18.2%); 51 follow-up specimens were collected ≈4–5 days after baloxavir or neuraminidase inhibitor therapy . HA phylogeny ...

  Abstract Highly pathogenic avian influenza (HPAI) H5N8 virus, first identified in late 2016 in Egypt, continues to circulate and has replaced the previously dominant HPAI H5N1 virus of clade 2.2.1. In this study, HPAI H5N8 was detected on 23 commercial poultry farms in Egypt . Complete genome sequences of three isolates collected in 2021 were obtained using next-generation sequencing (NGS) and subjected to genetic characterization. Phylogenetic analysis showed these isolates to belong to clade 2.3.4.4b, comprising two genotypes: EA-2021-Q and EA-2020-A . Molecular analysis of the haemagglutinin (HA) protein revealed the presence of T156A and V538A substitutions in the duck isolate and an N183S substitution in the chicken isolate . Several additional nonsynonymous mutations were identified, including 147I and 504V in the PB2 protein , 127V, 672L, and 550L in the PA protein , 64F and 69P in the M2 protein , and 42S in the NS1 protein . Comparative analysis of HA antigenic sites bet...

  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...

  {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 ____

  Abstract Avian influenza (AI) is a significant disease affecting chickens and other avian species. Wild birds are thought to contribute to the virus transmission. The present study intends to explore the existence of AI type A virus in wild birds at the Six April Zoo, Khartoum State, Sudan . A total of 42 cloacal and tracheal swabs were collected from clinically healthy individuals belonging to five different wild bird species . The selected wild bird species were Common crane Grus grus, Sudan crowned crane Balearica pavonina, Helmeted guinea fowl Numida meleagris, Duck sp. Anatidae and Chestnut-billed sand grouse Pterocles exustus . Swabs were examined for AI virus antigen using the agar gel immunodiffusion (AGID) test, and all tested swabs produced positive results . The swab samples were inoculated into embryonated chicken eggs. The isolated virus was identified by AGID test and polymerase chain reaction . The virus was isolated from swabs collected from Grus grus, Balearica p...

  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...

  {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 Background :  Genomic surveillance of human seasonal influenza viruses is an essential component of the Global Influenza Surveillance and Response system (GISRS) and informs the recommendations for the seasonal influenza vaccine composition. Phylogenetic analysis of viral genome sequences is used to identify groups of viruses sharing potential antigenic change and computational models are used to predict which viral variants are likely to circulate at high levels in upcoming seasons. To facilitate discussion and reporting of genetic diversity , as well as to communicate antigen recommendations , up-to-date and sufficiently granular definitions of genetic clades are important.  Methods :  A nomenclature system for segments 4 (haemagglutinin) and 6 (neuraminidase) of human A(H3N2), A(H1N1)pdm09, and influenza B .  Results :  We devised a clade suggestion algorithm that proposes new subclades based on criteria including (i) the number of sequences i...

  {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 ____

  {Summary} Time Period: November 16, 2025 - November 22, 2025 -- H5 Detection :  6 site(s) ( 1.4% ) -- No Detection :  410 site(s) ( 98.6% ) -- No samples in last week :  50 site(s) (...) Source:  Link:  https://www.cdc.gov/nwss/rv/wwd-h5.html ____