Spatiotemporal dynamics of the unprecedented chikungunya outbreak in Guangdong, China.

In 2025, Guangdong province, China, experienced an unprecedented autochthonous chikungunya outbreak associated with a cluster of imported cases. We analyzed weekly city-level surveillance data and found that the outbreak exhibited a distinct two-peak pattern, with an initial outbreak in Foshan city followed by a larger outbreak in the neighbouring city of Jiangmen, together contributing more than 80% of the 23,464 confirmed cases reported in Guangdong. Space-time analysis identified five significant clusters, including two single-city hotspots corresponding to Foshan (July 20-August 16) and Jiangmen (September 14-October 18), suggesting a possible spatial shift in epidemic hotspots over time. In addition, we analyzed daily district-level surveillance data from Foshan and Jiangmen and fitted exponential models to the declining phase of the epidemic. The estimated decay rates were -0.118 in Foshan and -0.142 in Jiangmen, corresponding to epidemic half-lives of 5.87 and 4.88 days, respectively. Overall, our study characterizes the spatiotemporal dynamics of the largest chikungunya outbreak documented in China to date and underscores the importance of strengthening surveillance of mosquito-borne viruses given their increasing transmission risk and complex transmission dynamics.