Search Results (774)

H9N2 low-pathogenic avian influenza viruses (LPAIV) represent an ongoing zoonotic threat due to their enzootic circulation in poultry, reassortment capacity, and increasing human transmission events. This study characterized three H9N2 isolates recovered from apparently healthy poultry in a Changchun live poultry market (September–November 2022) that exhibited unprecedented genetic and phenotypic characteristics indicating enhanced zoonotic risk. Phylogenetic analysis showed a complex mosaic genome combining segments from four distinct lineages: HA from the BJ/94-like lineage (human-associated), PB1/NP/NS from the F98-like lineage, NA from the FJ/30-C-like branch, and PB2/M genes from the G1-like lineage. Bayesian molecular clock analysis estimated the most recent common ancestor at February 2022, with HL55 and HL56 diverging by May 2022, indicating rapid local viral evolution. All isolates retained hallmark LPAIV characteristics (monobasic HA cleavage site, zero intravenous pathogenicity index in chickens). However, receptor-binding assays demonstrated a critical divergence among the isolates: while HL45 exhibited exclusive avian α2-3 receptor preference, both HL55 and HL56 retained strong avian receptor binding while additionally showing measurable affinity for human α2-6 receptors-a dual-binding phenotype associated with enhanced zoonotic potential. Most significantly, the HL55 isolate successfully infected BALB/c mice without prior adaptation, causing transient upper respiratory tract replication, moderate weight loss (~9.2%), and mild disease without mortality or systemic dissemination. These findings demonstrate that the direct mammalian infectivity of this specific mosaic H9N2 lineage adds to the growing body of evidence regarding the zoonotic potential of contemporary H9N2 variants. The presence of known mammalian-adaptation markers (PB2 A588V, NA stalk deletion, HA position 226 leucine), combined with demonstrated dual receptor-binding capacity and inherent mammalian infectivity, underscores the accelerated evolutionary trajectory of H9N2 viruses toward increased zoonotic competence. These findings warrant intensified surveillance in live poultry markets, comprehensive antigenic characterization of emerging variants, and enhanced biosecurity measures to mitigate the risk of spillover events and potential pandemic emergence. Full article

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. Full article

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. Full article

The highly pathogenic H5 subtype avian influenza viruses (AIVs) pose persistent threats to the poultry industry and public health owing to their high lethality and pandemic potential. Migratory wild birds play a pivotal role in the global dissemination and genetic reassortment of the virus, serving as both natural reservoirs and long-distance vectors that drive its spatiotemporal spread. However, the extent and evolutionary drivers of antigenic divergence among H5 AIVs circulating in wild birds in East China remain poorly understood. Here, we aim to characterize the evolutionary dynamics and antigenic divergence of H5 AIVs isolated from wild birds in East China between 2013 and 2022. Whole-genome sequencing and phylogenetic analysis revealed that the isolates belonged to multiple clades, including 2.3.2.1 and 2.3.4.4, and encompassed the H5N1, H5N6, and H5N8 subtypes. Key amino acid site analysis showed that the glycosylation site patterns in the HA and NA proteins varied among clades, with some strains exhibiting gains or losses of glycosylation sites, while certain strains had acquired mutations associated with mammalian adaptation. Cross-hemagglutination inhibition (HI) assays combined with antigenic cartography demonstrated that the majority of the isolates were antigenically well-matched with the contemporaneous vaccine strains used in China, indicating that these vaccines effectively covered the predominant circulating antigenic variants at the time. Nevertheless, potential antigenic mismatches were still observed between some circulating strains and these vaccine strains. These findings suggest that wild birds in East China may contribute to the regional movement and diversification of H5 AIVs, highlighting the value of sustained surveillance for early warning and vaccine strain evaluation. Full article

Avian influenza viruses (AIVs) are widely distributed and have a wide range of hosts. Recently, the number of cases of infection associated with the circulation of highly pathogenic avian influenza H5N1 2.3.4.4b has raised concerns about its high transmission capacity in birds and mammals. This study analyzed swabs from bird and mammal species from the coast of Paraná and the northwest region of São Paulo, Brazil, for the presence of AIV in animals that did not present clinical or histopathological lesions of infection that indicated the need for molecular characterization during monitoring. Of the 661 animals analyzed, three tested positive, two of which were birds (Sula leucogaster and Thalasseus acuflavidus) while one was a mammal (Otaria flavescens) (0.45%, CI 95%: 0.16–1.33). A complete genome sequence of H5N1 AIV was obtained from a brown booby (Sula leucogaster) from the Paraná coast (GISAID accession number: EPI_ISL_1897537). Our study reinforces the importance of continuous genomic surveillance, especially in AIV hosts that do not show signs of infection, to enhance the One-Health assessment approach. Full article

Highly pathogenic avian influenza (HPAI) A(H5N1) viruses of clade 2.3.4.4b have recently spread across the Americas, prompting intensified surveillance efforts in Brazil aimed at early detection in wild birds. As part of these efforts, we identified a low pathogenic avian influenza A(H11N2) virus in a white-rumped sandpiper (Calidris fuscicollis) sampled at Lagoa do Peixe National Park (PNLP) in southern Brazil. Whole-genome sequencing revealed that seven of the eight gene segments shared high nucleotide similarity (approximately 98.8%) with viruses previously detected in shorebirds from Delaware Bay, North America. In contrast, the PB1 segment showed high nucleotide similarity (approximately 99%) to the PB1 lineage associated with clade 2.3.4.4b A(H5N1) genotype B3.2 viruses circulating in the Americas. Phylogenetic, nucleotide identity, and molecular clock analyses indicated that this lineage shares a recent common ancestor with North American LPAI viruses and was subsequently detected in distinct viral genetic backgrounds. Although no HPAI virus was identified in this study, the presence of a PB1 segment related to H5N1-associated lineages suggests that genetic components linked to these viruses were circulating among low pathogenic avian influenza viruses in South America. These findings highlight the importance of continued surveillance in migratory bird populations to improve understanding of avian influenza virus diversity and support epidemiological monitoring. Full article

Background/Objectives: Emerging viral zoonoses represent a growing threat to global public health, with most newly emerging infectious diseases originating from animal reservoirs. Recent outbreaks of monkeypox, Ebola virus disease, Marburg virus disease, Rift Valley fever, and avian influenza highlight the capacity of zoonotic viruses to cross species barriers, spread internationally, and generate substantial health, social, and economic consequences. This review examines the ecological, epidemiological, and biological determinants of viral zoonotic emergence and transmission, with particular emphasis on vaccination and outbreak prevention strategies. Methods: A structured narrative review was conducted using a predefined literature search strategy across major scientific databases. Peer-reviewed epidemiological, clinical, and public health publications published between January 2000 and February 2026 were screened and selected according to predefined relevance criteria. Results: The emergence of viral zoonoses is driven by complex interactions among animal reservoirs, environmental and climatic changes, human behavior, and viral adaptation. Although transmission pathways and clinical outcomes differ among pathogens, common determinants of spillover and outbreak amplification were identified. Current evidence supports the importance of integrated surveillance, genomic monitoring, vaccination strategies, and community engagement as key components of preparedness and response. Emerging preventive approaches targeting pathogen transmission, including transmission-blocking strategies and vector-associated microbiota interventions, may provide additional opportunities for disease control. Conclusions: Strengthening preparedness for emerging viral zoonoses requires coordinated One Health approaches integrating human, animal, and environmental health. Future priorities include the development of next-generation vaccines, expansion of digital and genomic surveillance systems, improved equitable access to vaccines, and innovative interventions aimed at reducing zoonotic spillover and interrupting pathogen transmission. Full article

Animal infectious diseases impose severe economic burdens on livestock industries, threaten wildlife populations, and compromise food security. Although vaccination remains the cornerstone of disease prevention, conventional vaccine platforms are often constrained by safety, efficacy, or manufacturing scalability. This narrative review provides a comprehensive analysis of the state of the art in herpesvirus-vectored vaccines for veterinary applications, focusing on five well-characterized alphaherpesviruses: Bovine herpesvirus type 1 (BoHV-1), Pseudorabies virus (PRV), Marek’s disease virus (MDV), Equine herpesvirus type 1 (EHV-1), and Duck enteritis virus (DEV). The intrinsic characteristics of herpesviruses, including large, stable genomes; the capacity for foreign gene insertion; broad host tropism; and the ability to elicit robust humoral and cellular immunity, are examined, and their performance is compared with that of traditional vaccine platforms. Key advances in vectored vaccine development are highlighted, from proof-of-concept studies to the creation of advanced multivalent constructs. These approaches demonstrate protective efficacy against a range of significant animal pathogens, including foot-and-mouth disease virus, porcine reproductive and respiratory syndrome virus, avian influenza virus, infectious bursal disease virus, and West Nile virus. The literature was identified through systematic searches of PubMed, Google Scholar, and Web of Science (1990–2026), followed by title/abstract screening and reference chaining. Future directions in vector engineering, mucosal delivery, and synthetic biology approaches are considered. Herpesvirus-vectored vaccines represent a versatile platform for enhancing animal health, supporting sustainable agriculture, and mitigating zoonotic risks. Full article

H9N2 avian influenza viruses inherently carry cross-species transmission potential, making continuous surveillance critical for pandemic prevention. This study focused on monitoring the 2024 H9N2 epidemic in Jiangsu Province’s external environment, analyzing its molecular evolution and receptor binding properties, assessing cross-species transmission and pandemic risks, and investigating serological antibody levels across different human populations. Environmental samples were collected from live poultry markets, farms, slaughterhouses, and bird habitats across Jiangsu, screened via quantitative PCR (qPCR), with positive samples used for virus isolation and whole-genome sequencing. Receptor binding properties were tested by hemagglutination assay, and H9N2 antibody levels were measured in 370 occupationally exposed individuals and 240 non-exposed individuals using hemagglutination inhibition (HI) assays. Among the 5779 collected samples, 6.89% tested H9N2-positive, and 12 strains belonging to the Eurasian lineage Y280-like clade G57 genotype were successfully isolated. All strains carried the HA-Q226L mutation, with 11 showing preferential binding to human α-2,6 receptors and one strain possessing dual receptor binding capability. Internal genes harbored mammalian adaptation mutations, and M2 proteins contained mutations conferring complete resistance to amantadine-class antiviral drugs. Serological tests revealed antibody positive rates of 4.05% in exposed populations and 2.5% in non-exposed populations, with no statistically significant difference between groups. These findings confirm that Jiangsu’s circulating H9N2 viruses have acquired human receptor preference and mammalian adaptation, posing silent infection and pandemic risks. Enhanced surveillance and the development of candidate vaccine stockpiles are strongly recommended. Full article

Highly pathogenic avian influenza (HPAI) is a lethal disease of poultry that has recently spilled over into mammals, including dairy cattle and humans, heightening concerns for livestock health, food security, and pandemic emergence. While vaccines that induce neutralizing antibodies against hemagglutinin and neuraminidase provide strain-specific protection, durable cross-subtype immunity requires T-cell responses targeting conserved internal antigens such as nucleoprotein (NP). To leverage these conserved targets, we utilized a previously engineered mosaic nucleoprotein (MNP) incorporating T-cell epitopes from thousands of influenza A virus (IAV) strains, conferring broad protection against epidemic (H3N2) and pandemic (H1N1) IAV in mice. Here, we tested whether precision adjuvancy could differentially imprint adaptive immunity to MNP in cattle. Combination formulations paired the carbomer-based nano-emulsion Adjuplex (ADJ) with either a STING agonist (cyclic dinucleotides; CdN) or a TLR4 agonist (glucopyranosyl lipid A; GLA) to program distinct inflammatory milieus. Both formulations elicited circulating IFN-γ–producing T cell responses and NP-specific antibodies in serum and milk. However, STING activation via CdN generated more potent and consistent cellular and humoral immunity than TLR4 engagement. These data demonstrate that selective activation of innate sensing pathways functionally imprints adaptive immune magnitude and quality in a large animal host. By advancing a broadly protective, T-cell-focused vaccine strategy in cattle, this work supports a One Health framework to mitigate H5N1 transmission risk at the human–animal interface. Full article

Avian influenza virus (AIV), a zoonotic pathogen capable of cross-species transmission, poses a significant global health threat due to its rapid evolutionary adaptation. This review consolidates evidence from the past decade on AIV-autophagy interactions, emphasizing mechanistic insights and therapeutic potential. Research indicates that various AIV strains can trigger autophagosome formation via viral components, although the completeness of autophagic flux is not fully understood. These virus–host interactions are notably influenced by viral genotypes (e.g., H5N1 vs. H9N2) and host species (avian vs. mammalian). Current studies suggest that modulating autophagy may reduce AIV-induced acute lung injury, with pharmacological agents showing potential in mitigating inflammatory responses. We systematically explore three research areas: (1) strain-specific mechanisms of autophagy induction, (2) host-specific autophagic responses in poultry and human models, and (3) the therapeutic potential of stage-specific autophagy manipulation. This synthesis clarifies critical knowledge gaps, particularly the need for standardized autophagic flux assessment in avian cells, while providing a conceptual framework for developing autophagy-targeted strategies against AIV pathogenesis. Full article

H3N2 subtype avian influenza virus (AIV) is prevalent in poultry and wild birds and typically causes asymptomatic or mild respiratory infections. However, genetic reassortment between H3N2 and other AIV subtypes generates novel strains capable of crossing the species barrier, posing a threat to both poultry and public health. In this study, nine H3N2 AIVs were isolated from ducks in live poultry markets (LPMs) in Guangxi, southern China, during 2022–2024. Phylogenetic analysis revealed that all eight gene segments of the nine isolates were clustered within the Eurasian lineage, with internal genes derived from multiple subtypes, including H1, H2, H3, H4, H5, H6, H7, and H9. These findings indicate complex gene reassortment of H3N2 AIVs in Guangxi. Importantly, the PB2 genes of certain isolates were closely related to those of highly pathogenic H5 subtype viruses, suggesting that H3N2 AIVs may contribute internal genes to H5 viruses. Three representative isolates (LZD44, NND98, and NND100) were assessed for pathogenicity in SPF chickens and mice. All three strains successfully replicated in the respiratory tissues of both species. Notably, the LZD44 virus, which harbored the mammalian-adaptive mutations PB2-MVV and NP-I353V, presented significantly higher virulence in chickens and mice than the other two strains. These results demonstrate that H3N2 subtype AIVs are capable of replicating in certain tissues of chickens and mice without prior adaptation, underscoring a potential risk for cross-species transmission. Consequently, sustained surveillance of H3N2 subtype AIVs is essential to prevent the spillover of novel recombinants into the human population. Full article

This method comparison demonstrated equivalent analytical and diagnostic performance of IndiMix JOE with intype IC-RNA as an alternative real-time polymerase chain reaction (RT-PCR) chemistry compared to the National Animal Health Laboratory Network (NAHLN) influenza A virus (IAV) RT-PCR surveillance assay using AgPath-ID One-Step RT-PCR Reagents in avian swabs and tissues and bovine milk. In avian samples, IndiMix JOE with intype IC-RNA using a fast reduced-volume protocol had comparable results to the NAHLN reference RT-PCR with and without intype IC-RNA using standard NAHLN thermocycling conditions. A six-way comparison of RT-PCR chemistries and exogenous internal controls in milk samples illustrated equivalent mean CT values (ANOVA, p = 0.9938). Additional experiments in avian swabs and tissues, bovine milk and semen samples resulted in comparable analytical sensitivity in limits of detection (LOD), linearity (R² > 0.977), and PCR efficiencies, and no significant differences in mean CT values (ANOVA, p > 0.05). Diagnostic performance showed 100% agreement across field and spiked sample matrices compared to the NAHLN reference method. The study supports the use of IndiMix JOE and intype IC-RNA as an alternative, with practical improvements relevant to surveillance workflows including enhanced testing flexibility, efficiency, outbreak response capacity, and reduced time to results. Full article

To address the lack of a commercially available vaccine for goose circovirus (GoCV), we developed and evaluated a prokaryotically expressed subunit vaccine targeting the viral capsid (Cap) protein. A truncated Cap protein (GoCV-ΔCap) was expressed in Escherichia coli (E. coli) and formulated with aluminum hydroxide as a subunit vaccine (GoCVsubvac). Goslings were primed intramuscularly (i.m.) with high (75 µg) or low (15 µg) doses GoCVsubvac, followed by a boost 14 days later. At 14 days post-boost, goslings were challenged with GoCV and were administered a bivalent inactivated vaccine against Newcastle disease virus (NDV) and H9-subtype Avian influenza virus (AIV). Using our established gosling pathogenicity model, vaccine efficacy was evaluated via body weight, lesions, viral load, antibody titers, cytokine responses, and interference with NDV/AIV immunity. Results demonstrated that the GoCV-ΔCap vaccine, especially the high-dose formulation, provided effective immunoprotection. It elicited robust humoral and cellular immune responses, reduced lymphoid pathology, and decreased the viral detection rate in lymphoid tissues from 100% (5/5) in infected controls to 40% (2/5). Importantly, it alleviated GoCV-induced immunosuppression and preserved the immunogenicity of co-administered vaccines. This novel subunit vaccine is a promising candidate for controlling GoCV disease (GoCVD). Full article

During 2022–2024, a highly pathogenic avian influenza virus (HPAIV) H5N1 strain, designated A/Seagull/Hebei/qhd6/2024 (H5N1), was isolated from migratory birds in Beidaihe National Wetland Park, North China. Phylogenetic analyses revealed that its hemagglutinin (HA) gene belongs to the 2.3.4.4b clade, while the neuraminidase (NA) gene and internal genes clustered with strains originating from multiple continents, consistent with a transcontinental reassortment event. The virus also exhibited 90.1–98.1% nucleotide homology with human-derived H5N1 isolates. Molecular characterization identified key virulence-associated mutations, including the classic HPAIV HA cleavage site, HA-T160A (associated with enhanced human receptor-binding capacity), and NA-I117T (potentially linked to drug resistance). BALB/c mouse infection experiments confirmed systemic replication and high pathogenicity of strain qhd6, with a 50% lethal dose (LD50) of 0.95 log₁₀EID₅₀/mL. Antigenic analysis revealed good cross-reactivity with the widely used H5-Re14 vaccine strain. This study reports the identification, in Beidaihe National Wetland Park, of an HPAIV H5N1 strain whose genetic characteristics suggest intercontinental reassortment and indicate cross-species transmission risk. It clarifies the genetic characteristics and pathogenicity of this strain, providing an important theoretical and practical basis for precise surveillance, risk early warning, and comprehensive prevention and control of AIV at migratory bird stopover sites in North China. Full article