ETIDIOH - NEW

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...

Abstract The highly pathogenic avian influenza (HPAI) subtype H5N1 is a severe viral disease which continues to pose a significant threat to public health and a rigorous understanding of its transmission dynamics across its major pathways is essential for developing effective control strategies . Phylogenetic analysis suggests that H5N1 spillover occurs primarily between wild and domestic birds . However, increasing contact between these species and humans increases the risk of zoonotic transmission . In this work, we develop a mathematical model to examine the transmission dynamics of H5N1 and evaluate the effectiveness of proposed control measures. The model employs a compartmental framework that includes human, domestic, and wild bird populations. We then use this model to estimate the basic reproduction number for each population group and perform a sensitivity analysis to assess the contribution of the parameters to the spread of the disease. Numerical simulations are also conduct...

Abstract While wild waterfowl are known reservoirs of avian influenza viruses and facilitate the movement of these viruses , there are notable differences in the response to infection across species. This study explored differential responses to infection with highly pathogenic avian influenza in Snow Geese (Anser caerulescens) located in the California Central Valley . Though H5 antibody prevalence was high across years among birds sampled in the winter (75% in both years via hemagglutination inhibition), these values were even higher among birds sampled in summer that failed to migrate (i.e., August 2023 = 100% and August 2024 = 93% via hemagglutination inhibition). Birds that failed to migrate were also generally lighter than birds sampled in the winter and presented notable damage to cerebrum and cerebellum . In December 2022, a single individual positive for infection with H5N1 at the time of sampling indicated reduced movement during the 14 days following sampling but completed s...

  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 ...

By Bengt Nyman from Vaxholm, Sweden - Larus canus 2203, CC BY 2.0,  https://commons.wikimedia.org/w/index.php?curid=49877446 Wild birds {Herring Gulls} found dead through SAGIR network. Source: WOAH,  https://wahis.woah.org/#/in-review/6672 ____

Abstract Avian influenza viruses undergo frequent genetic reassortment, which can coincide with phenotypic changes in transmission, pathogenicity, and host species niche . Since 2020, clade 2.3.4.4b H5 high pathogenicity avian influenza viruses (HPAIVs) have driven a global panzootic , causing mass mortality in wild birds, poultry , and, for the first time, repeated spillover infections in a variety of mammalian species . This resurgence of H5 HPAIV has coincided with a dramatic increase in the number of circulating reassortant strains ; however, the scale, impact and drivers of these reassortants remain unknown. Here, we combined statistical and phylodynamic modelling to reconstruct the global evolutionary dynamics of H5Nx viruses across four epizootic seasons (2020-2024). We identified 209 genetically distinct reassortants , stratified into three transmission categories based on their phylogenetic and epidemiological profiles. Accounting for sampling depth and HPAIV incidence, we est...

Abstract Introduction :  In 2023 and 2024, mass mortalities of swans occurred on the Caspian coast of Kazakhstan , which affected more than seven hundred birds of a local population of 10–15 thousand. It is widely known that viral infections significantly affect the microbiome content of various organisms , but the influence of H5N1 infection in the gut microbiota of wild birds remains little studied. Almost no information is available on postmortem microbial changes after the devastating impact of H5N1 influenza. Methods :  In addition to standard routine virological studies , we were interested in investigating the microbiological changes resulting from infection with the highly pathogenic H5N1 using 16S rRNA gene sequencing. Results :  Virological studies of samples taken from the dead swans identified the highly pathogenic influenza virus H5N1 subtype as the primary cause of mortality. 16S analysis of samples from freshly dead swans revealed patterns of microbial dysb...

Abstract Since 2021, highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b virus has affected wild bird populations globally . Griffon vultures (Gyps fulvus), a species hitherto considered unexposed, experienced an HPAI H5N1 outbreak in 2022 in southern Europe , leading to moderate mortality and reduced breeding success . The integration of virological, serologic, phylogenetic, and ecologic data revealed a short yet intense viral circulation and a probable common source of infection . The dissemination across Spain and France was likely caused by frequent interpopulation movements of birds. This integrated overview of the 2022 HPAI outbreak in vultures provides novel insights into the role of large-scale movements of wild birds in the spread of such disease. Understanding the epidemiologic dynamics of HPAI H5N1 in these scavenger species is crucial because the birds play vital roles in ecosystem functioning. Their susceptibility to this virus highlights potential broader ecol...

  By Scott Wieman - Own work, CC BY-SA 3.0,  https://commons.wikimedia.org/w/index.php?curid=24620634 A wild Herring Gull in Nordland Region. Source: WOAH,  https://wahis.woah.org/#/in-review/6621 ____

Di dierat-stock - Crow-1, CC BY 3.0,  https://commons.wikimedia.org/w/index.php?curid=33155653 A wild Carrion Crow in Khabarovsk Region. Source: WOAH,  https://wahis.woah.org/#/in-review/6622 ____

Abstract H5Nx clade 2.3.4.4b high pathogenicity avian influenza viruses (HPAIV) have been detected repeatedly in Great Britain (GB) since autumn 2020, with H5N1 dominating detections but with low level detection of H5N5 during 2025. Globally, these viruses have caused mass mortalities in captive and wild avian and mammalian populations , including terrestrial and marine mammals . H5N1 has been the dominant subtype, and whilst incursions have overlapped temporally, occurrences have often been spatially distinct. Here, we report the detection of a mortality event in wild birds on the Norfolk coastline in the east of England, where H5N1 HPAIV was detected in five Great Black-backed Gulls (Larus marinus) and a Northern Fulmar (Fulmarus glacialis). Interestingly, at the same site, and as part of the same mortality event, a total of 17 Great Black-backed Gulls, one Herring Gull (Larus argentatus), one Atlantic Puffin (Fratercula arctica) and one Northern Fulmar tested positive for H5N5 HPAIV...

ABSTRACT In recent years, high pathogenicity avian influenza viruses (HPAIVs) have spread among wild, captive, and domestic birds, as well as mammals . Beyond the resulting economic and ecological losses , spillover into mammals has raised concerns about a potential pandemic . Viral tropism refers to the spectrum of host species, organs, and cells susceptible and permissive to viral infection . It is a potent driver of infection dynamics and shedding patterns, which presents important variations both between and within hosts: in poultry, HPAIV leads to systemic endothelial infection in domestic chickens , whereas neurological and selective epithelial infections are observed in domestic ducks . In mammals , infection can result in respiratory and neurological disease , but the recent outbreaks in domestic dairy cows highlighted a unique and remarkable adaptation to the mammary gland prone to viral shedding in milk. The present review explores viral tropism of HPAIV across recent spillov...

  By Alexis Lours - Own work, CC BY 4.0,  https://commons.wikimedia.org/w/index.php?curid=138694692 ___ A Yellow-legged Gull in Leiria Region. Source: WOAH,  https://wahis.woah.org/#/in-review/6609 ____

Abstract In 2024, we sequenced highly pathogenic avian influenza virus A(H5N1) clade 2.3.4.4b genomes isolated from 5 brown skuas from James Ross Island , Antarctica . Phylogenetic analysis suggested the virus reached Antarctica through South America . Continued genetic surveillance will be critical to elucidate H5N1 virus transmission dynamics within Antarctica and surrounding areas. Source: US Centers for Disease Control and Prevention,  https://wwwnc.cdc.gov/eid/article/31/8/25-0186_article ____

Abstract We analyzed 15 cases of highly pathogenic avian influenza (HPAI) clade 2.3.4.4b virus infections detected in wild birds in South Korea during September 2023–March 2024. We isolated and sequenced 8 H5N1 and 7 H5N6 viruses . We investigated spatiotemporal transmission dynamics by using a Bayesian discrete trait phylodynamic model that incorporated geographic and host species information. Our source–sink dynamics support introductions of H5N1 viruses from northern Japan to South Korea and subsequent spread through multiple regions in South Korea. The H5N6 viruses were most likely introduced into southwestern South Korea and spread northeastward. Wild waterfowl, especially wild ducks , played a key role in transmission of both H5N1 and H5N6 viruses. Our data showed multiple introductions and extensive spread of HPAI clade 2.3.4.4b viruses and bidirectional transmission between Japan and South Korea. Our results highlight the value of enhanced active surveillance for monitoring HPA...

Abstract The November 2021 introduction of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b into North America triggered a devastating outbreak , affecting more than 180 million domestic birds and spreading to more than 80 wildlife species across Canada and the US . From this outbreak, we have sequenced 2955 complete A( H5N1 ) viral genomes from samples collected in Canada and, in conjunction with previously published data, performed multifaceted phylodynamic analyses. These analyses reveal extensive diversification of A(H5N1) viruses via reassortment with low-pathogenic avian influenza viruses. We find evidence of repeated ancestral strain replacement by direct descendants, indicative of compounding viral fitness increases . Spatiotemporal modeling identified critical geographic areas facilitating transcontinental spread and demonstrated genotype-specific host dynamics, offering essential data for ongoing control and prevention strategies. Source: Science Advances,  https:...

Summary The recent emergence of highly pathogenic H5N1 avian influenza virus infections in dairy cows and humans in the U.S. has raised alarms regarding the potential for a pandemic . Over 995 dairy cow herds and at least 70 humans have been affected, including cases of severe disease and the first reported H5N1-related death in the U.S . Sporadic human infections with no known contact with infected animals highlight the possibility of viral adaptation for efficient human-to-human transmission. Concurrently, the virus continues to circulate in wild birds, backyard flocks, and hunted migratory species , further amplifying the risk to humans and domestic animals. This article provides an overview of the current outbreak status , emphasizes the importance of robust surveillance systems to detect emerging strains with pandemic potential, and highlights risks to the U.S. dairy and poultry industries. Recommendations for risk mitigation include enhanced biosecurity measures, improved surveil...

By © Giles Laurent, gileslaurent.com, License CC BY-SA, CC BY-SA 4.0,  https://commons.wikimedia.org/w/index.php?curid=142133890  A wild Golden Eagle in Lapin aluehallintovirasto Region. Source: WOAH,  https://wahis.woah.org/#/in-review/6597 ____

  By Andreas Trepte - Own work, CC BY-SA 2.5,  https://commons.wikimedia.org/w/index.php?curid=10944563 A Great black-backed Gull in Nordland Region. Source: WOAH,  https://wahis.woah.org/#/in-review/6594 ____

Abstract Wild waterbirds are circulating important RNA viruses, such as avian coronaviruses, avian astroviruses, avian influenza viruses, and avian paramyxoviruses . Waterbird migration routes cover vast territories both within and between continents. The breeding grounds of many species are in the Arctic, but research into this region is rare. This study reports the first Newcastle disease virus (NDV) detection in Arctic Russia . As a result of a five-year study (from 2019 to 2023) of avian paramyxoviruses and avian influenza viruses in wild waterbirds of the Taimyr Peninsula , whole-genome sequences of NDV and H3N8 were obtained . The resulting influenza virus isolate was phylogenetically related to viruses that circulated between 2021 and 2023 in Eurasia, Siberia, and Asia. All NDV sequences were obtained from the Herring gull, and other gull sequences formed a separate gull-like clade in the sub-genotype I.1.2.1, Class II. This may indirectly indicate that different NDV variants ad...