Active surveillance for emerging influenza A viruses – Findings from a One Health study in Vietnam’s live bird markets

Vuong N. Bui, Oguzie, J.U., Tung D. Dao, Anh N. Bui, Son D. Tran, Quy D. Nguyen, Hung Q. Nguyen, Trujillo-Vargas, C.M., Marushchak, L.V., Thang Nguyen-Tien, Shittu, I., Hung Nguyen-Viet, Phuc Duc Pham, Huy C. Nguyen, Brooks, J.S. and Gray, G.C. 2025. Active surveillance for emerging influenza A viruses – Findings from a One Health study in Vietnam’s live bird markets. International Journal of Infectious Diseases 161: 108132.

Abstract/Description

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.