Spatiotemporal dynamics and genotypic shift of Coxsackievirus A16 in Fujian, China, from 2010 to 2025.

INTRODUCTION: Despite the diverse etiology of hand, foot, and mouth disease (HFMD), Coxsackievirus A16 (CVA16) persists as a dominant pathogen in the Asia-Pacific region. This study characterizes the molecular epidemiological evolution of CVA16 in Fujian Province from 2010 to 2025 to understand its changing prevalence and genetic evolution. METHODS: We analyzed the temporal, spatial, and demographic distributions of CVA16-HFMD in Fujian Province from 2010 to 2025, and further investigated the phylogenetic characteristics via MEGA and BEAST software. RESULTS: From 2010 to 2025, laboratory-confirmed CVA16 cases accounted for 25.96% of HFMD pathogen spectrum in Fujian, with periodic biennial fluctuations characterized by increases in even-numbered years and decreases in odd-numbered years and a post-2023 surged to >50%. CVA16 Cases peaked during spring-summer, with a male-to-female ratio of 1.69:1, predominantly in children aged 1-3 years. Genetically, B1 subgenotype (cluster B1a-c) co-circulated. B1b dominated before 2018, gradually shifting to B1a thereafter, and to B1c (emerging in late 2023) after mid-2023. CONCLUSION: These findings clarify the long-term distribution and genetic shifts of CVA16 in Fujian, identifying the emerging B1c as a major driver of recent outbreaks and providing a baseline for regional HFMD prevention and vaccine development.