Contribution of climate change to the spatial expansion of West Nile virus in Europe

West Nile virus (WNV) is an emerging mosquito-borne pathogen in Europe where it poses a growing public health threat. Although climate change has been proposed as a driver of its spatial expansion, a formal causal attribution has been lacking. This study quantifies the extent to which the spatial expansion of WNV in Europe can be attributed to climate change while accounting for other human influences such as land-use and population change. Ecological niche models predicting risk of local WNV circulation leading to human cases were trained and then used to compare factual simulations with a counterfactual climate in which long-term trends were removed. Results show a notable increase in the area ecologically suitable for WNV circulation during 1901–2019 under observed climate, whereas suitability remains largely unchanged in the no-climate-change counterfactual. The sharp rise in the population at risk reflects both population growth and climate change, with the latter emerging as a critical driver of heightened WNV circulation risk in Europe.