ETIDIOH - NEW

  Abstract Since March 2024, HPAI H5N1 virus has infected dairy cattle in the U.S., prompting concern about novel transmission routes . During an outbreak in California , HPAI H5N1 RNA was detected in an asymptomatic bull's semen . Although infectious virus was not isolated , questions remain about semen-associated transmission risks and biosecurity practices. Competing Interest Statement The authors have declared no competing interest. Source: BioRxIV,  https://www.biorxiv.org/content/10.1101/2025.10.16.682947v1 ____

  Abstract The emergence of H5N1 highly pathogenic avian influenza virus (HPAIV) clade 2.3.4.4b in dairy cattle across multiple U.S. states in early 2024 marks a major shift in the virus’s host range and epidemiological profile . Traditionally limited to bird species , the ongoing detection of H5N1 in cattle , a mammalian host not previously considered vulnerable, raises urgent animal and human health concerns about zoonoses and mammalian adaptation . We assessed the feasibility of using commercially available pasteurized milk as a sentinel matrix for the molecular detection and genetic characterization of H5N1 HPAIV. Our aim was to determine whether retail milk could serve as a practical tool for virological monitoring and to evaluate the use of full-length genome segment amplification for extracting genomic sequence information from this highly processed matrix. Our results link HPAIV sequences in store-bought milk to the cattle outbreak and highlight both the potential and the l...

  ABSTRACT The global spread of the A/goose/Guangdong/1/96-lineage H5N1 highly pathogenic avian influenza (HPAI) viruses has been accompanied by an expanded host range and the establishment of sustained viral transmission among dairy cattle . To evaluate if the evolving H5N1 viruses have changed tissue tropism over time , we compared the binding patterns of recombinant hemagglutinin (HA) proteins derived from clade 1 (A/Vietnam/1203/04, H5VN) and circulating clade 2.3.4.4b viruses detected from wild bird (A/Eurasian Teal/Hong Kong/AFCD-HKU-23-14009-01020/2023, H5HK) and dairy cattle (A/bovine/Ohio/B24OSU-439/2024, H5OH). The HA protein of A(H1N1)pdm09 virus was included for comparison . Using bio-layer interferometry , H1 protein preferentially bound to the α2,6-linked sialoside 6′SLNLN , while H5 proteins preferentially bound to the α2,3-linked sialoside 3′SLN . H5OH showed higher binding affinity to 3′SLN than H5HK and H5VN. The attachment patterns of H1 and H5 proteins to the re...

  Abstract Since its discovery in U.S. dairy cattle in early 2024, the highly pathogenic H5N1 avian influenza (clade 2.3.4.4b) has spread widely among herds, causing major economic losses. This zoonotic event emphasizes the urgent need for H5 vaccines that elicit strong, durable, cross-reactive immune responses in cattle , especially young calves. To address this, we immunized mice and cattle with a centralized consensus H5 vaccine, designed to localize to the central node of the human H5 phylogenetic tree . The vaccine was delivered using serotype-switched adenoviral vectors in a prime:boost regimen , combined with intramuscular and intranasal coadministration to target systemic and mucosal immunity and elicit strong humoral and cellular immune responses. This approach strategically integrates multiple innovative features: centralized consensus immunogens, mucosal targeting, and vector serotype switching that are aimed at maximizing immune protection against H5N1 viruses . Our res...

  Abstract Highly pathogenic avian influenza virus of the H5N1 subtype has been infecting U.S dairy cattle and spreading among dairy farms since March 2024 . H5N1 surveillance systems for dairy farms are needed, but information on whether environmental sampling can inform these systems is lacking. To guide a surveillance framework , we determined the environmental locations on H5N1-affected dairies (n = 25) in four states (California, Colorado, Michigan, and Ohio) that harbored influenza A virus (IAV), and explored sample characteristics that may influence viral detection. A total of 623 samples from environments and sale barns were characterized for IAV and classified into six categories based on location. A total of 94 samples ( 15.1% ) had IAV detected , the majority in the following categories: milking equipment/personal protective equipment , parlor surfaces , and wastewater/lagoons/manure . These results suggest that dairy environments most likely to harbor IAV are those with...

  Abstract The incursion of high pathogenicity avian influenza A virus (IAV) into US dairy cows is unprecedented in the era of molecular diagnosis and pathogen sequencing. This raises questions over the likelihood of further outbreaks and whether dairy cattle could be a mixing vessel for novel strains of IAV. Using a panel of BSL2-safe reassortant viruses representing clade 2.3.4.4b H5 epizootic lineages circulating since 2020, we found that a cow B3.13 isolate displayed enhanced replication in cow mammary gland cells , along with increased viral polymerase activity and stronger interferon antagonism in cow cells compared to an earlier EA-2020-C genotype virus. However, multiple avian and mammalian IAV strains , including other clade 2.3.4.4b high pathogenicity genotypes, were replication competent in bovine cells, particularly those of the mammary gland , suggesting that there is a diverse circulating IAV pool with the potential to infect cows. Moreover, we show that cow mammary c...

  Abstract The circulation of highly pathogenic H5 influenza A viruses in cattle , other mammals, and wildlife threatens animal and human health. To address this, we vaccinated heifer-calves with a deactivated rabies-virus-based H5 vaccine , which was well-tolerated and elicited neutralizing antibodies against both clade-1 and clade-2.3.4.4b H5N1 viruses, comparable to naturally H5-infected and convalescing cows. The immune responses to the vaccine platform were durable for at least 200 days and unaffected by preexisting RABV immunity. Source: npj Vaccines,  https://www.nature.com/articles/s41541-025-01238-2 ____

Abstract In early 2024, an unprecedented outbreak of H5N1 high pathogenicity avian influenza was detected in dairy cattle in the USA . As of mid-2025 the epidemic is ongoing, resulting in spillbacks into poultry, wild birds and other mammals including humans . Here, we present molecular and virological evidence that the cattle B3.13 genotype H5N1 viruses rapidly accumulated adaptations in polymerase genes that enabled better replication in bovine cells and tissues, as well as cells of other mammalian species including humans and pigs . We find evidence of several mammalian adaptations gained early in the evolution of these viruses in cattle including PB2 M631L , which is found in all cattle sequences, and PA K497R , which is found in the majority. Structurally, PB2 M631L maps to the polymerase-ANP32 interface, an essential host factor for viral genome replication . We show that this mutation adapts the polymerase to better interact with bovine ANP32 proteins , particularly ANP32A, and ...

  ABSTRACT Influenza A virus (IAV) infection of the respiratory tract can cause both respiratory and non-respiratory symptoms . Gastrointestinal (GI) symptoms such as diarrhea, vomiting, and abdominal pain can occur in persons with seasonal influenza A or novel IAV infections , but the extent to which IAVs can infect and replicate in GI tissues is understudied. The ongoing outbreak of A( H5N1 ) IAV in US dairy cattle associated with sporadic human infections has highlighted the potential public health threat posed by the introduction of infectious virus into materials that may be consumed by humans , such as milk. Here, we review epidemiologic reports documenting the frequency of GI complications in humans infected with seasonal and novel IAVs and present laboratory studies supporting the capacity of IAV to replicate in mammalian GI tissues , with an emphasis on A(H5N1) viruses. Studies assessing the ability of IAV to cause mammalian infection following consumption of virus-contain...

  ABSTRACT The mammary gland is an essential organ for milk production, providing essential immune and nutritional support to offspring and supplying dairy products for human consumption. In both humans and animals , the lactating mammary gland is susceptible to bacterial and viral infections , which can lead to mastitis and, in some cases, vertical transmission to offspring , with potential adverse effects on infant health. However, until recently, the role of respiratory viruses in mammary gland infection has been relatively understudied, particularly their ability to infect mammary epithelial cells and transmit through lactation. The recent emergence of highly pathogenic avian influenza H5N1 clade 2.3.4.4b in dairy cattle has demonstrated the virus’s capacity to replicate in the mammary gland, cause mastitis, and produce high viral loads in milk . This raises significant concerns about the potential for zoonotic transmission to humans and other animals in contact with infected d...

ABSTRACT The 2.3.4.4b clade highly pathogenic avian influenza H5N1 infected diverse non-human mammalian species , gained mammal-to-mammal transmission potential , and caused sporadic human infections . However, whether non-human mammals enable the human adaptation of 2.3.4.4b H5N1 to establish human infections is unclear. Gain-of-function research restrictions may hinder the assessment of 2.3.4.4b H5N1 human adaptations. Here, we tracked the evolution of 2.3.4.4b H5N1 that infected non-human mammals and evaluated their ability to gain human adaptations. The non-human mammal 2.3.4.4b H5N1 partly acquired classical human-adapting mutations , which are identical to the residues of H1N1pdm09 and seasonal human H3N2 viruses, while showing a few species-specific adaptations that might be potential barriers for successful human infections. The polymerase complex proteins , PA and PB2, acquired human adaptations in non-human mammals, with fox-infected viruses showing more positive selection in...

  ABSTRACT The H5N1 strain of influenza A virus (IAV) continues to cause severe infections in a range of avian and mammalian species , including sporadic but concerning cases in humans. There is growing concern that circulating H5N1 strains could lead to widespread human outbreaks . Research with highly pathogenic H5N1 viruses is restricted to Biosafety Level 3 (BSL-3) laboratories. Vesicular stomatitis virus (VSV)-based vaccine vectors expressing heterologous viral proteins from Ebola, SARS-CoV-2, Lassa virus, etc., have previously been shown to be safe and effective in animal models and human clinical trials . Here, we report the development of a recombinant VSV expressing the hemagglutinin (HA) and neuraminidase (NA) genes of H5N1 IAV (H5N1-VSV), which serves as a versatile platform to study various aspects of H5N1 IAV biology. H5N1-VSV replicated robustly to titers comparable to those of the full H5N1 virus in multiple cell lines. In mice , H5N1-VSV vaccination was safe, elicit...

Abstract Transmission routes of highly pathogenic H5N1 between cows or to humans remain unclear due to limited data from affected dairy farms. We performed extensive air, farm wastewater, and milk sampling on 14 H5N1 positive dairy farms across two different California regions. Virus was detected in the air in milking parlors and from exhaled breath of cows . Infectious H5N1 virus was detected in the air and water streams ; sequence analysis revealed viral variants on a farm in these locations. Longitudinal analysis of milk from the individual quarters of cows revealed a high prevalence of subclinical H5N1 positive cows and a heterogeneous distribution of infected quarters that maintained a consistent pattern over time. Our data highlight potential modes of H5N1 transmission on dairy farms. Competing Interest Statement SSL and LCM receive funds from Flu Lab and NIH. ASL receives funds from Flu Lab, NIH, and CDC. ASL receives consulting fees and research support from Roche, outside of t...

Abstract In 2024, highly pathogenic avian influenza A H5N1 caused outbreaks in wild birds, poultry, cows, and other mammals in the United States with 61 human cases also reported by the CDC. Detection of influenza A H5 RNA in wastewater has been previously reported in sewersheds in Texas and North Carolina with nearby impacted dairy herds following the emergence of H5N1 in dairy cows. Here, we conduct retrospective testing of total influenza A and H5 hemagglutinin genes in wastewater as well as present and apply new assays for detection of H1 and H3 genes across a respiratory virus season in an urban California sewershed from September 2023 to May 2024. Total influenza A, H1, and H3 were regularly detected, while H5 was first detected in March . We developed a model that uses Monte Carlo simulations and previously published parameters to estimate the numbers of infected people, poultry, wild birds, or liters of H5-contaminated milk required to result in measured H5 concentrations in wa...

  Key points   -- At the present time , based on available information, FAO-WHO-WOAH assess the global public health risk of influenza A(H5) viruses to be low , while the risk of infection for occupationally or frequently exposed (e.g., with backyard poultry) persons is low to moderate depending on the risk mitigation and hygiene measures in place and the local avian influenza epidemiological situation.  -- Transmission between animals continues to occur and, to date, a growing yet still limited number of human infections are being reported. Although additional human infections associated with exposure to infected animals or contaminated environments are expected to occur, the overall public health impact of such infections at a global level , at the present time, is considered minor . The assessment could change if and when additional epidemiological or virological information becomes available.  -- This risk assessment from FAO, WHO and WOAH updates the assessment ...