Genetic characteristics and phylogenetic analysis of coxsackievirus A6 isolated in Linyi, China, 2022-2023.

Hand, foot and mouth disease (HFMD) was one of the most common infectious disease in the past few decades. After 2013, coxsackievirus A6 (CVA6) has replaced enterovirus 71 (EV-A71) and coxsackievirus A16 (CVA16), becoming the predominant pathogen responsible for HFMD in many areas in China. The objective of this study is to investigate the genetic characteristics and molecular epidemiology of CVA6 in Linyi from 2022 to 2023. A total of 965 HFMD cases were enrolled in this study and analyses based on VP1 nucleotide sequences were performed to determine the evolutionary trajectory of CVA6. In 2022, 281 (281/386, 72.8%) were positive for enterovirus (EVs), and 217 (217/281, 77.2%) were CVA6 positive. In 2023, 398 (398/579, 68.7%) samples were positive for EVs, and 243 (243/398, 61.1%) were CVA6 positive. Six sequences were selected from each year for the homology analysis. The results showed that 12 strains isolated in Linyi were far from the prototype strain (AY421764) and the first CVA6 strain reported in China (JQ364886). Phylogenetic analysis showed that the CVA6 strains isolated in Linyi all belonged to D3 subgenotype. CVA6 is emerging as a common pathogen causing HFMD in Linyi, and continuous surveillance of HFMD etiological agents is necessary.