Modelling and forecasting a potential chikungunya outbreak in France, 2025

Mainland France is experiencing an unprecedented number of autochthonous cases of chikungunya in multiple locations, primarily in southern France, likely linked to the recent outbreak in La Réunion and associated travel. Given the region’s suitable climate and the widespread and abundant presence of Aedes albopictus , the primary European mosquito vector of chikungunya, further cases are anticipated in the coming months. Here, we apply a state-of-the-art, climate-sensitive eco-epidemiological model to forecast chikungunya transmission dynamics at affected outbreak locations. With a 2–3-month lead time in predictions of peak transmission, the model identifies foci most likely to experience severe outbreaks (e.g., Salon-de-Provence, Bernis, Castries) this year and helps to inform prioritisation and public health impact.