tetano
Editor, Senior Moderator
Transbound Emerg Dis
. 2026;2026(1):4393527.
doi: 10.1155/tbed/4393527.
Dong-Yeop Lee 1 , Sori Kim 1 , Sun-Hak Lee 1 2 , Andrew Y Cho 1 2 , Heesu Lee 1 2 , Nyamsuren Otgontogtokh 1 2 , Ye-Ram Seo 1 2 , Kai-Yun Tan 1 , Sae-Hyeon Park 2 , Ji-Yeong Kim 1 , Yongwoo Son 1 , Wonjun Sung 1 , Chang-Seon Song 2 , Dong-Hun Lee 1
Affiliations Expand
H9N2 avian influenza viruses (AIVs) continue to cause disease in poultry and pose a zoonotic risk. In South Korea, live bird markets (LBMs) serve as evolutionary epicenters for H9N2 AIVs, facilitating interspecies transmission and genetic reassortment. To improve surveillance efficiency, environmental sampling was conducted at two LBMs in Korea between November 2023 and May 2025. A total of 486 samples, comprising 190 poultry swab samples, 179 environmental samples, and 117 tissue samples, were collected. A sample was considered positive when virus isolation in embryonated eggs yielded hemagglutination-positive allantoic fluid that was subsequently confirmed as AIV by matrix (M)-gene real-time reverse transcription PCR (rRT-PCR). Drinking water showed the highest AIV isolation rate (15.7%). Whole-genome sequencing of 45 isolates revealed that all viruses belonged to clade B4.6.1 of the B-lineage (formerly Y280). Phylogenetic analysis suggested the presence of two distinct temporal clusters: the 2023 cluster, which was not detected after November 2023, and the 2024-2025 cluster, which appeared to continue circulating in Korean LBMs. A historical reassortment involving PB1 and PA segments from clade B4.7 H9N2 viruses was inferred to have occurred prior to the introduction of the B-lineage into Korea. An isolate (N22-97) exhibited evidence of reassortment between the temporal clusters within clade B4.6.1: its PA segment clustered with the 2024-2025 viruses, whereas the remaining segments clustered with the 2023 viruses. Multiple mammalian-adaptive mutations (e.g., HA-226L and PB2-598I) were identified, with genetic variation observed in drinking water-derived isolates. Single nucleotide variant (SNV) analysis revealed HA-A190T/V and HA-V318I variants, suggesting the presence of mixed viral populations within LBM environments. Sequence-based antigenic mapping identified five putative antigenic clusters, with most isolates-including the current Korean B-lineage vaccine strain-grouping within the dominant cluster. These findings highlight drinking water as a useful environmental matrix for AIV monitoring and underscore the value of environmental genomic surveillance for AIV detection in LBMs.
Keywords: avian influenza; environmental surveillance; genomic analysis; live bird market; phylogenetics.
. 2026;2026(1):4393527.
doi: 10.1155/tbed/4393527.
Environmental Contamination and Rapid Evolution of H9N2 Avian Influenza Virus in Live Bird Markets, South Korea, 2023-2025: Implications for Zoonotic Risk
Dong-Yeop Lee 1 , Sori Kim 1 , Sun-Hak Lee 1 2 , Andrew Y Cho 1 2 , Heesu Lee 1 2 , Nyamsuren Otgontogtokh 1 2 , Ye-Ram Seo 1 2 , Kai-Yun Tan 1 , Sae-Hyeon Park 2 , Ji-Yeong Kim 1 , Yongwoo Son 1 , Wonjun Sung 1 , Chang-Seon Song 2 , Dong-Hun Lee 1
Affiliations Expand
- PMID: 43004647
- PMCID: PMC13748803
- DOI: 10.1155/tbed/4393527
Abstract
H9N2 avian influenza viruses (AIVs) continue to cause disease in poultry and pose a zoonotic risk. In South Korea, live bird markets (LBMs) serve as evolutionary epicenters for H9N2 AIVs, facilitating interspecies transmission and genetic reassortment. To improve surveillance efficiency, environmental sampling was conducted at two LBMs in Korea between November 2023 and May 2025. A total of 486 samples, comprising 190 poultry swab samples, 179 environmental samples, and 117 tissue samples, were collected. A sample was considered positive when virus isolation in embryonated eggs yielded hemagglutination-positive allantoic fluid that was subsequently confirmed as AIV by matrix (M)-gene real-time reverse transcription PCR (rRT-PCR). Drinking water showed the highest AIV isolation rate (15.7%). Whole-genome sequencing of 45 isolates revealed that all viruses belonged to clade B4.6.1 of the B-lineage (formerly Y280). Phylogenetic analysis suggested the presence of two distinct temporal clusters: the 2023 cluster, which was not detected after November 2023, and the 2024-2025 cluster, which appeared to continue circulating in Korean LBMs. A historical reassortment involving PB1 and PA segments from clade B4.7 H9N2 viruses was inferred to have occurred prior to the introduction of the B-lineage into Korea. An isolate (N22-97) exhibited evidence of reassortment between the temporal clusters within clade B4.6.1: its PA segment clustered with the 2024-2025 viruses, whereas the remaining segments clustered with the 2023 viruses. Multiple mammalian-adaptive mutations (e.g., HA-226L and PB2-598I) were identified, with genetic variation observed in drinking water-derived isolates. Single nucleotide variant (SNV) analysis revealed HA-A190T/V and HA-V318I variants, suggesting the presence of mixed viral populations within LBM environments. Sequence-based antigenic mapping identified five putative antigenic clusters, with most isolates-including the current Korean B-lineage vaccine strain-grouping within the dominant cluster. These findings highlight drinking water as a useful environmental matrix for AIV monitoring and underscore the value of environmental genomic surveillance for AIV detection in LBMs.
Keywords: avian influenza; environmental surveillance; genomic analysis; live bird market; phylogenetics.