Evolving #dynamics of #H5Nx avian #influenza in #China revealed by long-term wild bird #surveillance

 

Abstract

H5Nx highly pathogenic avian influenza viruses pose persistent threats to poultry, wildlife, and public health. Over the past two decades, their geographic and host ranges have expanded across migratory networks whose epidemiological connectivity has become increasingly apparent through recent surveillance and genomic analyses. To elucidate these dynamics, we conduct long-term nationwide wild-bird surveillance in China, integrating active and passive monitoring. Our analyses reveal the maintenance, reassortment, and transmission of H5Nx viruses in wild birds, highlighting the value of sustained surveillance in capturing viral evolution. We identify distinct ecological patterns among major clades, with 2.3.4.4b showing the widest distribution and acting as the main lineage mediating intercontinental spread. Since 2020, most 2.3.4.4b viruses detected in wild birds in China have clustered with lineages originating outside China, consistent with repeated reintroduction rather than sustained local circulation. This shift underscores the growing role of migratory connectivity in shaping global viral exchange and the need for coordinated international active surveillance.

Source: 

Link: https://www.nature.com/articles/s41467-026-76039-9

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Rapid #Expansion of Highly Pathogenic Avian #Influenza #H5N1 Clade 2.3.4.4b Genotype #D1.1 Virus across #Flyway Regions, North #America, Fall 2024

 

Abstract

Highly pathogenic avian influenza clade 2.3.4.4b virus continues to circulate in North America and has caused severe human disease. That clade includes genotype D1.1, which became dominant in birds in late 2024. Recent phylodynamic reconstructions place D1.1 emergence in mid-2024 but differ on its inferred origin and early dissemination pathways. We combined targeted surveillance of wild birds in Arizona with publicly available US clade 2.3.4.4b hemagglutinin sequences to estimate when D1.1 genotype emerged and to infer its diffusion among the 4 major US flyways. Phylodynamic analyses showed transitions concentrated among adjacent flyways regions, consistent with stepwise dissemination during fall 2024 and limited support for long-distance Pacific–Atlantic exchange. The Pacific Flyway showed patterns consistent with an early source and the Central Flyway with a secondary hub linked to onward spread. Our findings support coordinated genomic surveillance across adjacent flyways to reduce detection delays and improve situational awareness during rapid viral expansion.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/32/8/26-0205_article

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Highly Pathogenic Avian #Influenza #H5N1 in South #America, 2022–2025: Spread, Affected Species, and Southward Expansion into the #Antarctic Region

 

Abstract

The H5N1 highly pathogenic avian influenza (HPAI) virus has caused severe global losses, reaching South America in 2022 and Antarctica in 2024. Here, we synthesize outbreak reports submitted to the World Organization for Animal Health by South American countries and overseas territories in this continent, and document the virus’s unprecedented expansion into Antarctica, affecting wild birds, wild mammals, and domestic poultry. Phylogenetic and time-calibrated Bayesian analyses were performed on available genomic sequences. Over 6 million domestic birds were lost, mostly from commercial operations. Of the 11 South American countries and overseas territories that reported H5N1 to WOAH, 10 reported infections in wild birds, spanning 104 species, 59.62% of which are migratory and predominantly non-trans-equatorial. Marine mammal outbreaks followed wild bird detections, with the South American sea lion (Otaria flavescens) being the most reported species. Several Antarctic bird species with migratory behavior were also reported in South America. Genomic analyses revealed multiple introduction events, regional viral diversification, and patterns consistent with repeated cross-species spillover events. These findings highlight H5N1’s extensive ecological reach in the Southern Hemisphere and underscore the urgent need for a One Health approach that strengthens wildlife and backyard-poultry surveillance, alongside coordinated regional action to control and prevent further HPAI spread.

Source: 

Link: https://www.mdpi.com/1999-4915/18/7/764

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Long-Term #Monitoring of #Influenza A Viruses in Wild #Waterfowl: Evidence from the Lake #Baikal Basin (2018–2024)

 

Abstract

Wild waterfowl constitute the primary natural reservoir of influenza A viruses, and wetlands at the convergence of major migratory flyways serve as critical hubs for viral genetic exchange. Baikal Siberia, situated at the intersection of the East African–West Asian, Central Asian, and East Asian–Australasian flyways, represents a unique yet understudied region in this context. Here we report the results of long-term virological surveillance of wild birds in the Lake Baikal basin conducted between 2018 and 2024. A total of 1036 cloacal swab samples from 28 bird species were screened, yielding 42 influenza A virus isolates belonging to 12 HA/NA subtype combinations: H1N1, H3N1, H3N2, H3N5, H3N6, H3N8, H4N6, H6N1, H6N2, H6N3, H6N8, and H12N5. Among the detected subtypes, H6 viruses—identified with four distinct neuraminidase combinations (N1, N2, N3, N8)—are of particular public health relevance owing to their documented capacity for dual-receptor binding and potential for zoonotic transmission to mammals, including humans. Full-genome sequencing followed by cluster analysis of internal gene segments identified 16 distinct segment constellations, indicating extensive reassortment. BLAST searches against the GISAID database revealed closest genetic relatives in Mongolia, South Korea, Japan, China, and Western Siberia, with more distant links to Bangladesh, Europe, and a possible intercontinental connection via the Pacific flyway. Maximum-likelihood phylogenetic analysis of the HA and NA segments confirmed that all isolates belong to the Eurasian genetic lineage, yet they are distributed across multiple clades rather than forming a single monophyletic group, reflecting the role of Buryatia as a mixing zone for genetically diverse viral populations. These findings substantially expand the understanding of influenza A virus ecology in the Lake Baikal basin and underscore the importance of continued surveillance at this key migratory crossroads in Northern Asia.

Source: 

Link: https://www.mdpi.com/1999-4915/18/7/761

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Inter-population #connectivity of southern elephant #seals and the likely intra-species #transmission #pathways of high pathogenicity avian #influenza

 

Abstract

High Pathogenicity Avian Influenza (HPAI) H5N1 clade 2.3.4.4b has spread beyond birds to affect seals across the Southern Ocean and sub-Antarctic region, with southern elephant seals (Mirounga leonina) particularly devastated. The virus, likely introduced via spillover from infected migratory birds, has killed tens of thousands of adult seals and pups throughout most of their range, though Macquarie Island remains unaffected so far. We used twenty years of elephant seal movement data from the southern Indian and Pacific oceans to assess whether seal-to-seal transmission could spread HPAI H5N1 between breeding colonies, despite the vast distances separating them (Marion Island, Iles Crozet, Iles Kerguelen, and Macquarie Island). There was substantial overlap in seals' at-sea distributions during their winter post-moult trips, when seals travel for weeks at average speeds of 3.5 km/h. Two transmission pathways were examined: (1) terrestrial "stepping stone" routes, where infected seals could pass the virus between colonies during short intervals to remain infectious were feasible from Marion Island to Kerguelen but not from Kerguelen to Macquarie Island; and (2) at-sea encounters between seals, which occurred frequently enough to enable transmission. The findings suggest that once established at Macquarie Island, the virus could potentially spread further to New Zealand's sub-Antarctic islands and mainland New Zealand. While seal-to-seal transmission appears possible, we conclude this is unlikely. Nonetheless, understanding at-sea contact rates enhances knowledge of H5N1 epidemiology and demonstrates the value of combining long-term population monitoring with movement data to understand wildlife disease dynamics.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Integrated Marine Observing System, https://ror.org/010x3gp67

CNRS

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.07.07.737127v1

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#Genomic and structural #evidence of #SARS-CoV-2 and #MERS-CoV in migratory #birds

 

Significance

Coronaviruses are regarded as highly important pathogens of birds and mammals. Herein, we obtained three almost full-length severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomes and one partial Middle East respiratory syndrome coronavirus (MERS-CoV) genome in the feces of migratory birds based on meta-transcriptome and PCR amplification. We determined the affinities and the complex structures between receptor-binding domain (RBD) of the SARS-CoV-2 viral spike protein and angiotensin-converting enzyme 2 (ACE2) protein of two migratory birds, Tundra and Black swans. Moreover, pseudotyped SARS-CoV-2 variants can enter into HeLa cells expressing ACE2 proteins of these birds. Altogether, our results expand our understanding of migratory birds as potential carrier of both SARS-CoV-2 and MERS-CoV.

Abstract

Migratory birds are the natural reservoir of influenza A virus (IAV), but their role as a carrier of SARS-CoV-2 remains unclear. Here, we report the identification of three almost full-length viral genome sequences of SARS-CoV-2 variants of concern (VOCs) in Tundra swans. These sequences are named hCoV-19/Tundra swan/Jiangxi/IMCAS_M1/2021 (IMCAS_M1), hCoV-19/Tundra swan/Jiangxi /IMCAS_M2/2021 (IMCAS_M2), and hCoV-19/Tundra swan/Jiangxi/IMCAS_M3/2021 (IMCAS_M3). IMCAS_M1 and IMCAS_M3 have the same mutations as the Beta VOC (K417N, E484K, and N501Y) in the receptor-binding domain (RBD) of the viral spike (S) protein, whereas IMCAS_M2 shares the same mutations as the Gamma VOC (K417T, E484K, and N501Y) in the RBD with all three showing their distinct mutations in the genomes. Virus receptor angiotensin-converting enzyme 2 (ACE2) proteins from both Tundra swan (tsACE2) and Black swan (bsACE2) can bind to the RBDs of all three viruses and the Alpha VOC, but not to RBD of the prototype (PT) virus. The polar contacts and hydrophobic interactions revealed by cryo-electron microscopy (cryo-EM) structures of the RBD–ACE2 complex, play key roles in virus–receptor engagement. Furthermore, HeLa cells expressing bsACE2 and tsACE2 proteins could be transduced by pseudotyped SARS-CoV-2 variants (Alpha, Beta, and Gamma) but not PT SARS-CoV-2. In addition, we obtained one partial genome of MERS-CoV named Bar-headed goose/Tibet/IMCAS_M4/2022 (IMCAS_M4) with 20,180 bp (~70.0% coverage). Our findings highlight the importance of migratory birds as potential carrier of both SARS-CoV-2 and MERS-CoV, thereby posing potential threat to public health.

Source: 

Link: https://www.pnas.org/doi/abs/10.1073/pnas.2400023123?af=R

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The Winners Take It All? #Global Evolutionary #Success of #H5Nx #Reassortants in the 2020–2024 #Panzootic

 

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 worldwide 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 unclear. 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 estimated that reassortants emerged most frequently from Asia, but `major' reassortants associated with increased host range, inter-seasonal persistence, and long-range dissemination, more frequently emerged from Europe. Altogether, reassortant emergence followed an episodic pattern in which most reassortants were transient, but 2% seeded large clusters of secondary reassortants soon after their own emergence. Statistical modelling revealed that reassortant success was strongly shaped by ecological factors, including sustained circulation in specific wild bird orders and detection across a wider range of host niches. Collectively, our findings uncover global reassortment dynamics in H5 HPAIVs and identify key virological and ecological drivers underpinning the emergence and spread of successful reassortants. These insights support the importance of enhanced surveillance to track evolution of H5 HPAIV and identify traits relevant for consideration in pandemic risk assessment.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Biotechnology and Biological Sciences Research Council, BB/V011286/1, BB/X006204/1, BB/X006166/1, BB/Y007271/1, BB/Y007298/1

Biotechnology and Biological Sciences Research Council - Institute Strategic Grants, BBS/E/RL/230002C, BBS/E/RL/230002D

Medical Research Council, MR/Y015045/1, MR/Y03368X/1

National Natural Science Foundation of China, https://ror.org/01h0zpd94, 32061123001, 32425053, 32200416

National Key Research and Development Program of China, 2023YFC2307500, 2024YFE0106000

European Union, 727922, 874850, 101094685, 101084171, 874735

Fonds National de la Recherche Scientifique, F.4515.22

Fonds voor Wetenschappelijk Onderzoek — Vlaanderen, G098321N

Source: 

Link: https://www.biorxiv.org/content/10.1101/2025.07.19.665680v2

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The #canine respiratory #epithelium is a permissive #ecosystem for #influenza interspecies #transmission and emergence

 

Abstract

The outcome of virus spillover ranges from dead-end infections to pandemics and is underpinned by host-pathogen interactions as well as evolutionary and epidemiological processes. The emergence of novel influenza A viruses (IAVs) has been associated with reassortment events involving multiple species, highlighting the importance of reservoir and intermediate hosts in viral emergence. Highly pathogenic H5N1 IAVs of the 2.3.4.4b genotype have caused a panzootic affecting a broad range of mammals. The role of dogs -arguably the most popular companion animal and a natural host of IAVs- in the ecology of IAVs under this new zooepidemiological scenario is unknown. To address this, we characterised the glycome of the dog respiratory epithelium, infected canine tracheal explants with multiple IAVs (including canine H3N2 and H3N8, equine H3N8, avian H3N8 and H5N1, swine H1N1, human H1N1 and H3N2, and bovine H5N1 viruses), and determined their cellular tropism. We show that the respiratory tract of dogs presents abundant sialylated glycans known to act as IAV receptors. Further, most IAVs (including 2.3.4.4b viruses) infected and replicated in dog tracheas, targeting mainly ciliated cells. Serological testing showed evidence of influenza spillover infections in dogs from the UK. Overall, our results show that the canine respiratory tract can provide a suitable environment for the generation of new IAVs. Given the multi-host contact networks of dogs in nature, they could act as recipients, bridging hosts, and/or mixing vessels for multiple IAV lineages, playing a central role in the ecology of influenza emergence.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Medical Research Council, https://ror.org/03x94j517, MR/Y03368X/1, MC_UU_0034/2, MC_UU_0034/3

Biotechnology and Biological Sciences Research Council, BB/Y007093/1, BB/Y007298/1, BBS/E/PI/230001A, BBS/E/PI/230002A, BBS/E/PI/230002B, BBS/E/PI/230001C

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.06.04.730051v1

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#Species - and #variant - specific #ACE2 compatibility shapes #SARS-CoV-2 #spillover potential in North American #cervids

 

Abstract

Free-ranging white-tailed deer (WTD) are established SARS-CoV-2 reservoirs, but the susceptibility of other cervid species remains unclear. Here we integrate receptor analysis, structural modeling, and field surveillance to assess SARS-CoV-2 susceptibility across North American cervids. We identify species- and variant-specific differences in ACE2–spike compatibility. Elk ACE2 exhibits weak binding to the ancestral strain (Wuhan-Hu-1) and Delta spike receptor-binding domains (RBDs), likely due to a unique K31N substitution. In contrast, it shows stronger binding to Alpha, Beta, Gamma, and Omicron RBDs containing N501Y. Biophysical assays, gel filtration chromatography, and cryo-EM confirm stable complex formation between elk ACE2 and Alpha RBD, but not RBD from the ancestral strain. Despite weak binding, elk ACE2 supports viral entry and replication in vitro. However, surveillance revealed limited evidence of infection in the United States, contrasting with widespread WTD transmissions. These findings demonstrate that ACE2 compatibility alone is insufficient to predict reservoir potential and provide a framework for assessing species susceptibility to emerging coronaviruses.

Source: 

Link: https://www.nature.com/articles/s41467-026-71623-5

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The #Mengla virus (Filoviridae: #Dianlovirus)

 

Abstract

Introduction. 

Filoviruses associated with various species of pteropodid bats (Chiroptera: Pteropodidae) are traditionally regarded as potential causative agents of hemorrhagic fevers with epidemic potential. The known agents of Ebola and Marburg fevers periodically cause sporadic cases and epidemic outbreaks in African countries. Recent discoveries of novel filoviruses associated with pteropodid bats in South and Southeast Asia highlight the necessity to investigate their genetic diversity and pathogenic potential.

The aim of this study was to investigate the genetic diversity and pathogenic potential of new filoviruses associated with bats, based on literature data.

Materials and methods. 

This review is based on an analysis of published literature describing the detection and molecular characterization of novel filoviruses identified in different geographic regions, with a particular focus on filoviruses associated with pteropodid bats in South and Southeast Asia. The analyzed studies include data on virus discovery, genome organization, taxonomic classification, and experimental assessment of biological properties. 

Results. 

Several novel filoviruses have been identified by metagenomic RNA sequencing of tissues from pteropodid bats captured in South and Southeast Asia. Among them, Mengla virus was detected in tissues of pteropodid bats (Rousettus spp.) captured in Mengla County, Yunnan Province, People’s Republic of China. Owing to a high level of genetic divergence, Mengla virus was classified as a representative of a new genus, Dianlovirus, within the family Filoviridae. Although a live isolate of Mengla virus has not yet been obtained, experimental studies using chimeric minigenome systems and virus-like particles suggest that the virus may exhibit tropism for tissues of various vertebrate hosts, including humans.

Conclusion. 

Members of the family Filoviridae are widely distributed within the geographic range of their natural reservoir–pteropodid bats–across South and Southeast Asia, including viruses evolutionarily related to Ebola and Marburg viruses. Although human disease caused by Mengla virus and other recently discovered filoviruses has not been documented, the potential for cross-species transmission and the emergence of novel filovirus infections in endemic regions remains.

Source: 

Link: https://virusjour.crie.ru/jour/article/view/16805

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Brown and Lesser #noddies as epidemiological #reservoirs and #sentinels of avian #influenza virus in the South-western Indian #Ocean

 

Abstract

Avian influenza virus (AIV) epidemiology is well documented in temperate regions but remains poorly understood in isolated ecosystems like tropical oceanic islands. On these islands, seabirds nest in dense interspecific colonies where the role of different species as reservoirs and dispersers of AIV may vary greatly. Here, we examine the role of noddies (Anous spp.) as potential reservoirs for low pathogenic AIV and evaluate their potential as sentinel species for highly pathogenic AIV introduction on tropical oceanic islands. We analyzed blood samples from 11 seabird species across eight islands in the southwestern Indian Ocean (2015 to 2020). Noddies exhibited high, stable seroprevalence (30 to 45%), comparable to reservoir host species in temperate regions. The detection of two N7 positive noddies, sampled the same year on two distinct islands, provided direct molecular evidence that AIV actively circulates on these island colonies. While most other species showed low exposure, Bridled Terns (Onychoprion anaethetus) had exceptionally high seroprevalence (80%), though their reservoir status requires further investigation due to limited sampling. Given noddies consistent exposure and regional distribution, we recommend prioritizing islands with large noddy populations for AIV surveillance. Continued investigation of viral dynamics within and among islands is now called for to elucidate the ecological drivers of AIV maintenance and transmission.

Competing Interest Statement

The authors have declared no competing interest.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.03.31.715511v1

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Three decades of #discovery: An overview of #Hendra virus, the original #Henipavirus

 

Abstract

Hendra virus (HeV) emerged in Australia in 1994, causing a devastating outbreak among horses in Brisbane with spread to humans, resulting in one death. This nonsegmented, negative-stranded RNA virus belongs to the family Paramyxoviridae and represents the first zoonotic paramyxovirus isolated from bats. Flying foxes (genus Pteropus) serve as the natural reservoir, with all four mainland Australian species carrying antibodies with no apparent disease. HeV initiates infection by binding ephrin-B2 receptors on vascular endothelial cells, driving characteristic pathology involving vasculitis, thrombosis, and neurological complications. Horses are amplifying hosts, shedding virus abundantly in respiratory secretions and posing transmission risks to humans during invasive procedures. To date, seven confirmed human infections have been documented, with a 57% fatality rate, presenting as severe respiratory disease or progressive encephalitis. Two genetic variants are now recognized: the original HeV genotype 1 and the emerging HeV genotype 2, identified in limited equine cases. Recent surveillance of bat roosts revealed substantial viral diversity, with peak shedding occurring during winter—coinciding with equine spillover peaks. Prevention integrates multiple strategies: the licensed equine vaccine Equivac which provides One Health protection for both horses and human contacts; biosecurity measures including proper PPE; and habitat restoration to reduce nutritional stress in bat populations. Emerging therapeutics include monoclonal antibodies, with m102.4 showing cross-protective activity against both HeV and the closely related Nipah virus. No licensed human vaccines currently exist, though candidates are in development. Future prevention strategies increasingly recognize the importance of Indigenous-led conservation approaches alongside biomedical interventions. This review will focus on the history of HeV, virus replication and diversity, epidemiology, clinical manifestations, diagnosis, treatment, prevention, as well as ecological and interdisciplinary countermeasures.

Author summary

Hendra virus (HeV) was first detected in 1994, with two outbreaks occurring within 2 months of that year. One was the index outbreak in the Brisbane suburb of Hendra, and the other was retrospectively diagnosed in the following year. This review examines the discoveries that have been made in the 30 years since its discovery.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014138

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#Dispersal, #adaptation and #persistence of #H5N1 in the sub-Antarctic and #Antarctica

 

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 risk of H5N1 endemisation, dispersal to other locations and ongoing evolution are highly concerning.

Competing Interest Statement

The authors have declared no competing interest.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.03.20.713283v1

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Dynamics and #control of highly pathogenic #H5 avian #influenza in a threatened #pelican population

 

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 during the outbreak is shown to have surprisingly little impact on mitigating the mortality; and current H5 vaccines relying on capture and injection to deliver cannot establish herd immunity in a wildlife population. The results provide the first field evidence supporting the hypothesis that viral fitness difference of H5N1 to previous H5NX subtypes is the key cause of the expanded epizootic and panzootic since 2022, and on highly debated HPAI management strategies in wildlife populations.

Competing Interest Statement

The authors have declared no competing interest.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.03.16.712014v1

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High pathogenicity avian #influenza in #pinniped #conservation

 

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 piece, we attempt to synthesize complexities at this intersection. We describe lessons learned from HPAIV investigations in marine wildlife, highlight gaps in knowledge and capacity, and discuss the incorporation of outbreak risk assessment and countermeasures into pinniped conservation. Finally, we propose ways in which pinnipeds—and marine wildlife broadly—could be better integrated into existing systems for HPAIV intelligence, control and prevention.

This article is part of the theme issue ‘Managing infectious marine diseases in wild populations’.

Source: 

Link: https://royalsocietypublishing.org/rstb/article/381/1945/20240320/480666/High-pathogenicity-avian-influenza-in-pinniped

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Multiple Introductions of Highly Pathogenic Avian #Influenza Viruses into the High #Arctic: #Svalbard and Jan Mayen, 2022 - 2025

 

Abstract

Between 2022 and 2025, highly pathogenic avian influenza viruses (HPAIVs) of clade 2.3.4.4b, including four distinct H5 Eurasian (EA) genotypes, were detected in wild birds and mammals in the Svalbard Archipelago and on the island of Jan Mayen. We describe their epidemiology and genomic characteristics to improve understanding of HPAIV occurrence and transmission in the High Arctic. The initial cases in 2022 occurred during summer and involved a glaucous gull (Larus hyperboreus) and great skuas (Stercorarius skua) on Svalbard and Jan Mayen, representing the first detections of HPAIVs in the High Arctic. Three HPAIV genotypes were identified: EA-2020-C (H5N1), EA-2021-AB (H5N1), and EA-2021-I (H5N5). In 2023, HPAIVs were detected in a broader range of bird species, and retrospectively in an Atlantic walrus reported by another research group (Odobenus rosmarus rosmarus). Genotypes identified in 2023 were EA-2020-C (H5N1), EA-2021-I (H5N5), and EA-2022-BB (H5N1). No cases were reported in 2024. In 2025, EA-2021-I (H5N5) was detected in Arctic foxes (Vulpes lagopus) on Svalbard, without preceding detections in wild birds. The foxes exhibited neurological symptoms, and necropsy of one individual revealed the presence of feathers in its stomach. All sequenced viruses from the Arctic foxes uniquely carried the combination of PB2-E627K and PB1-H115Q, which is associated with mammalian adaptation. The detection of multiple genotypes indicates repeated and independent introductions of HPAIVs into these regions. The co-circulation of genetically distinct virus strains in areas of high bird density further suggests that Arctic breeding grounds may facilitate local viral amplification, reassortment, and subsequent dissemination along migratory flyways, including transcontinental spread.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

EU4Health, 101132473

The Research Council of Norway, https://ror.org/00epmv149, 352880

The SEAPOP program, 192141

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.02.17.706283v1

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Foraging #ecology drives viral community structure in #NZ's aquatic #birds

 

Abstract

Wild migratory birds play a major role in the global spread of viruses, yet the diversity, host range and transmission patterns of viruses harboured by migratory species in Aotearoa/New Zealand remain largely unknown. This knowledge gap is critical given New Zealand's position along major migratory flyways spanning Oceania, Antarctica and east Asia, where understanding viral diversity is key to assessing the risk of viral introductions such as highly pathogenic avian influenza virus and viral dispersal across these regions. To address this, we conducted the first large-scale metatranscriptomic survey of wild birds from New Zealand and its subantarctic islands, collecting 1,348 samples from 31 host species spanning four avian orders. We identified 118 avian viruses from 17 families, including 107 novel species, greatly expanding our knowledge of avian viral diversity. Viral communities differed significantly by host order and foraging behaviour, with scavenger birds harbouring more diverse viromes than non-scavengers. Although no HPAI subtypes were detected, we recovered a low-pathogenic avian influenza A/H1N9 virus from red knots (Calidris canutus) and a divergent tobanivirus from Auckland Island teal (Anas aucklandica), the first putative avian member of the Tobaniviridae. Notably, we detected 12 mammalian-associated viruses, primarily in scavenger birds, including Hedgehog hepatovirus, Rabbit haemorrhagic disease virus 2, and sea lion astroviruses, with mammalian host reads confirming their dietary origin. This study establishes the first virome baseline for New Zealand's migratory birds, highlighting the ecological role of foraging in shaping viral communities and improving regional preparedness for HPAI and other emerging avian pathogens.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Te Niwha, New Zealand's Infectious Disease Research Platform, TN/SWC/24/UoOJG

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.09.693119v1

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#Ecology of low pathogenicity avian #influenza virus #H7 in wild #birds in south-eastern #Australia prior to emergence of high pathogenicity avian influenza H7 in #poultry

 

Abstract

Adding to the global burden of high pathogenicity avian influenza (HPAI) H5N1, an unprecedented five HPAI H7 outbreaks occurred globally in 2024. Of these, three occurred in southeast Australia, with the independent emergence of HPAI H7N9, H7N8, and H7N3, resulting in the destruction of 2 million poultry. Historical data demonstrates that H7 outbreaks in Australia do not occur randomly, rather, there is a strong association between the timing of the previous H7 outbreaks and rainfall patterns in southeastern Australia. We aimed to address a hypothesis wherein prior to H7 outbreaks in poultry, there was a detectable change in H7 prevalence and/or virus diversity in wild bird populations. We addressed this using virological and serological surveillance data generated from multiple programs. Despite the collection of thousands of samples, there was only weak evidence to support our hypothesis, which provides strong incentive to evaluate current surveillance approaches for the purposes of risk prediction. However, in alignment with a previous analysis, there is strong support for a relationship between H7 outbreak probability and rainfall patterns across southeast Australia. Overall, improved understanding of the ecology and evolution of H5 and H7 viruses in wild bird reservoirs is pivotal to global disease preparedness and response.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Australian Department of Agriculture Fisheries and Forestry

Australian Department for Health and Aged Care

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.08.693062v1

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#Ecology and #environment predict spatially stratified #risk of #H5 highly pathogenic avian #influenza clade 2.3.4.4b in wild #birds across #Europe

 

Abstract

Highly pathogenic avian influenza (HPAI) represents a threat to animal and human health, with the ongoing H5N1 outbreak within the H5 2.3.4.4b clade being one of the largest on record. However, it remains unclear what factors have contributed to its intercontinental spread. We use Bayesian additive regression trees, a machine learning method designed for probabilistic modelling of complex nonlinear phenomena, to construct species distribution models (SDMs) for HPAI clade 2.3.4.4b presence. We identify factors driving geospatial patterns of infection and project risk distributions across Europe. Our models are time-stratified to capture both seasonal changes in risk and shifts in epidemiology associated with the succession of H5N6/H5N8 by H5N1 within the clade. While previous studies aimed to model HPAI presence from physical geography, we explicitly consider wild bird ecology by including estimates of bird species richness, abundance of specific taxa, and “abundance indices” describing total abundance of birds with high-risk behavioural traits. Our projections of HPAI clade 2.3.4.4b indicate a shift in persistent, year-round risk towards cold, low-lying regions of northwest Europe associated with H5N1. Methodologically, we demonstrate that while most variation in risk can be explained by climate and physical geography, adding host ecology is a valuable refinement to SDMs of HPAI.

Source: 

Link: https://www.nature.com/articles/s41598-025-30651-9

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Unpacking the #extinction #crisis: rates, patterns and causes of recent extinctions in #plants and #animals

 

Abstract

Biodiversity loss is one of the greatest challenges facing Earth today. The most direct information on species losses comes from recent extinctions. However, our understanding of these recent, human-related extinctions is incomplete across life, especially their causes and their rates and patterns among clades, across habitats and over time. Furthermore, prominent studies have extrapolated from these extinctions to suggest a current mass extinction event. Such extrapolations assume that recent extinctions predict current extinction risk and are homogeneous among groups, over time and among environments. Here, we analyse rates and patterns of recent extinctions (last 500 years). Surprisingly, past extinctions did not strongly predict current risk among groups. Extinctions varied strongly among groups, and were most frequent among molluscs and some tetrapods, and relatively rare in plants and arthropods. Extinction rates have increased over the last five centuries, but generally declined in the last 100 years. Recent extinctions were predominantly on islands, whereas the majority of non-island extinctions were in freshwater. Island extinctions were most frequently related to invasive species, but habitat loss was the most important cause (and current threat) in continental regions. Overall, we identify the major patterns in recent extinctions but caution against extrapolating them into the future.

Source: Proceedings of the Royal Society, Biological Sciences, https://royalsocietypublishing.org/doi/full/10.1098/rspb.2025.1717

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