Abstract
WHAT IS ALREADY KNOWN ABOUT THIS TOPIC? The circulating strain in the recent Chikungunya fever outbreak in Guangdong Province belongs to the East/Central/South African (ECSA) genotype. However, the specific mutations in the viral genome remained unclear. WHAT IS ADDED BY THIS REPORT? This study conducted whole-genome sequencing of viral sequences from clinical samples. The results confirmed that the epidemic strain belongs to the Middle African Lineage (MAL) within the ECSA genotype, not the Indian Ocean Lineage (IOL). Further analysis of nucleotide mutations revealed several adaptive mutations compared with the S27 genomic sequence (NC_004162), such as E1-A226V, E2-L210Q, and E2-I211T. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE? 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 Aedes albopictus 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, Ae. albopictus is the predominant mosquito species, while the distribution of Ae. aegypti is relatively limited. The ecological predominance of Ae. albopictus likely serves as a key contributing factor facilitating the rapid importation and subsequent widespread dissemination of the current epidemic strain.