Molecular Epidemiology and Evolution of Swine Influenza A Viruses, Vietnam, 2020–2024

The research focused on genomic surveillance of swine influenza A viruses (IAV-S) in Vietnam during 2020–2024. Researchers analyzed 56 virus isolates (21 H1N1, 31 H1N2, and 4 H3N2) and identified multiple co-circulating H1 and H3 clades, including pandemic H1N1, Eurasian avian-like, and European lineages. Three H1 clades were found exclusively in Vietnam and circulated for up to 12 years. Analysis revealed multiple independent introductions of viruses from North America, Europe, China, Thailand, and Cambodia. Researchers detected extensive genetic reassortment frequently involving internal genes of pandemic H1N1 virus. The findings underscore the need for sustained IAV-S surveillance in Vietnam.