Active surveillance for emerging influenza A virus: findings from a one health study in Vietnam's live bird markets.

Abstract

OBJECTIVES: Live bird markets (LBMs) in Asia have often been the source of human infections with avian influenza virus (AIV). METHODS: From July 2021 to August 2023, we employed a One Health approach in conducting periodic surveillance for novel influenza A viruses in five LBMs in northern Vietnam. Specimens were studied with egg culture, molecular assays, Sanger sequencing, and next-generation sequencing. RESULTS: We studied a total of 688 human, avian, and bioaerosol specimens. Among these, 118 (17.2%) were found to have molecular evidence of AIVs. Next-generation sequencing of 92 isolates revealed multiple AIV subtypes, including H4N6 (n = 1), H5N1 (n = 3), H5N8 (n = 6), H6N2 (n = 3), H6N6 (n = 18), and H9N2 (n = 61) and mix infections (n = 7). Our H5Nx sequences belonged to the Eurasian lineage clade 2.3.4.4b, while our H6N2 sequences were of group III, H6N6 of group II, and H9N2 of the BJ94-lineage clade 4.6.14. CONCLUSIONS: The relatively high prevalence of AIV, particularly highly pathogenic H5N1 and H5N8 viruses, along with the subtype diversity, frequent co-infections and notable mutations, highlights the urgent need for continued monitoring and control of AIV in Vietnam's poultry farms and LBMs.