Outbreak of Chikungunya Virus with <i>Aedes albopictus</i>-Adaptive Mutations — Guangdong Province, China, 2025

Based on previous genomic surveillance and pathogen studies, mutations like E1-A226V, E2-L210Q, and E2-I211T were generally considered characteristic of IOL within the ECSA genotype and are known to enhance viral replication and transmission efficiency in <i>Aedes albopictus</i> mosquitoes. This study identifies the circulating strain in Guangdong belongs to MAL, which is phylogenetically distinct from IOL, yet also carries these mutations. This suggests these may represent adaptive changes in the MAL strain to a new mosquito host. In Guangdong Province, <i>Ae. albopictus</i> is the predominant mosquito species, while the distribution of <i>Ae. aegypti</i> is relatively limited. The ecological predominance of <i>Ae. albopictus</i> likely serves as a key contributing factor facilitating the rapid importation and subsequent widespread dissemination of the current epidemic strain.