Evolutionary dynamics of coxsackievirus A24 variant associated with acute hemorrhagic conjunctivitis in Brazil

Coxsackievirus A24 variant (CVA24v) is a major etiological agent of acute hemorrhagic conjunctivitis (AHC), a highly contagious viral illness with the potential for widespread outbreaks. Although it has spread globally, especially in Asia, there is limited information on its evolutionary dynamics in South America. In this study, we examined 107 complete VP1 gene sequences, including 38 Brazilian isolates gathered from 1987 to 2020, to explore the phylogenetic, molecular, and geographic patterns of CVA24v circulation. Phylogenetic analyses revealed at least four CVA24v independent introduction events into Brazil over the past four decades, with the most recent being linked to strains from French Guiana and Mexico. Bayesian inference based on the VP1 gene estimated the time to the most recent common ancestor (tMRCA) around 1966 and a global substitution rate of 6.196 × 10⁻³ substitutions/site/year. Migratory reconstructions found Asia as a central hub of viral spread, with significant routes connecting Brazil to multiple continents. Population dynamics investigations revealed that successive introductions lead to increased genetic diversity. These findings highlight the recurrent reemergence of CVA24v in Brazil and underscore the importance of genomic surveillance in controlling AHC outbreaks. This work contributes to a deeper understanding of CVA24v transmission dynamics, providing important insights for future outbreak mitigation.