The 2025 Chikungunya Outbreak in Guangdong Province, China, and the Emerging Multi-pathogen Arboviral Threat in the Pearl River Delta.

Background From mid-June into late December 2025, China experienced its largest-ever Chikungunya virus (CHIKV) outbreak across Guangdong Province, a densely populated region of southeast China with extensive international travel and established Aedes mosquito populations. CHIKV, dengue virus (DENV), and Zika virus (ZIKV) share the same Aedes vectors, overlap in clinical presentation, and exhibit serologic cross-reactivity. We describe the epidemiology and integrated public health response to this outbreak, as well as future arboviral risks and mitigation strategies. Materials and methods We synthesized weekly surveillance data from the Guangdong Provincial Center for Disease Control and Prevention, national epidemiological and genomic data from the China CDC and World Health Organization, Hong Kong Observatory climate records, published literature, and government bulletins. Outbreak dynamics were analyzed using confirmed-case counts disaggregated by prefecture-level city and reporting week. Results Guangdong reported over 25,800 locally transmitted CHIKV cases across all 21 prefecture-level cities, with nationwide cases exceeding 29,500. The outbreak occurred in two distinct waves: an initial wave centered on Foshan City (July-August; 8,948 cases) that was successfully contained through a rapid, multi-level public health response; and a second, larger wave in Jiangmen City (September-October; 10,035 cases) temporally coincident with three tropical cyclones that made landfall within a 16-day span, creating widespread Aedes breeding habitat. No deaths were reported in Guangdong. The causative lineage was the Middle African Lineage within the East/Central/South African genotype, carrying Aedes albopictus-adaptive mutations (E1-A226V, E2-L210Q, E2-I211T) independently acquired through convergent evolution with the Indian Ocean Lineage. The persistence of cases into mid-December, combined with the warmest winter on record in the Pearl River Delta, raises concerns about overwintering mosquitoes and an early resurgence in 2026. Conclusions The 2025 Guangdong outbreak suggests that extreme weather events can overwhelm even well-executed arboviral responses and that the climate-vector-arbovirus interface represents a systems-level vulnerability requiring anticipatory preparedness. We advocate for typhoon-landfall-triggered vector control deployment, intensified genomic and entomological surveillance beginning in spring 2026, multiplex molecular diagnostics for concurrent CHIKV/DENV/ZIKV detection, obstetric and neonatal arboviral screening, and cross-jurisdictional coordination across the Pearl River Delta and beyond.