Evolution and spatio-temporal dynamics of Enterovirus A71 subgenogroups in Vietnam

BackgroundEnterovirus A71 (EV-A71) is the major cause of severe hand, foot and mouth disease and viral encephalitis in children across the Asia-Pacific region, including in Vietnam which has experienced a high burden of disease in recent years. Multiple subgenogroups (C1, C4, C5 and B5) concurrently circulate in the region with a large variation in epidemic severity. The relative differences in their evolution and epidemiology were examined within Vietnam and globally. MethodsA total of 752 VP1 gene sequences were analysed (413 generated in this study combined with 339 obtained from GenBank), collected from patients in 36 provinces in Vietnam during 2003andndash;2013 along with epidemiological metadata. Globally representative VP1 gene datasets of subgenogroups were used to co-estimate time-resolved phylogenies and relative genetic diversity to infer virus origins and regional transmission network. ResultsDespite frequent virus migration between countries, the highest genetic diversity of individual subgenogroups was maintained independently for several years in specific Asian countries representing genogroup-specific sources of EV-A71 diversity. ConclusionThis study highlights a persistent transmission network of EV-A71, with specific Asian countries seeding other countries in the region and beyond, emphasising the need for improved EV-A71 surveillance and detailed genetic and antigenic characterisation.</p