Surveillance and control efficacy of the Bergerac, France, 2025 chikungunya outbreak

The spread of the highly invasive mosquito, Aedes albopictus, across Europe, combined with climate change and human travel and trade, has led to new epidemic threats from mosquito-borne viruses, most significantly dengue and chikungunya, which are increasing in frequency and magnitude. In 2025, mainland France has seen a record number of autochthonous cases and outbreaks of chikungunya, spread across multiple locations, primarily introduced by travellers from the French Overseas Territory of La Reunion which is experiencing severe chikungunya outbreaks. Here, we describe one of the largest French outbreaks and subsequent control measures in the city of Bergerac, Dordogne, which resulted in 102 cases as of 5th November 2025. Using a state-of-the-art mathematical model, we accurately predict the course of the outbreak, suggesting that the initial control measures in the first four weeks after the discovery of the outbreak, limited in their intervention radius, had little effect on reducing the number of cases, given the high incidence and the wide geographic extent of viral circulation. However, subsequent more widespread and intense control efforts, combined with likely increased public awareness, substantially reduced case numbers. These findings underscore the need to tailor control measures to intensity and scale of viral circulation combined with effective preventive and proactive arbovirus surveillance. We conclude that adulticides combined with public awareness campaigns can be effective for public health protection and are an important part of mitigating against the risk of Aedes-borne arboviruses and the ongoing outbreaks in mainland France.