West Nile virus cases reach record high in France

France has recorded a record number of autochthonous West Nile virus cases, with 117 infections identified in mainland France between early May and September 21, 2026. According to Santé publique France, this represents a 27% increase from the previous week, with 25 new cases detected in the most recent seven-day period.

The virus has spread across 21 departments and seven regions, including Provence-Alpes-Côte d'Azur, Occitanie, Île-de-France, Auvergne-Rhône-Alpes, Nouvelle-Aquitaine, and for the first time, Pays de la Loire and Centre-Val de Loire.

West Nile virus is transmitted to humans via Culex mosquitoes that have fed on infected birds. While most infections are asymptomatic or resemble flu-like illnesses, approximately 1% of cases can lead to severe, potentially fatal neurological complications, particularly in elderly or immunocompromised individuals. There are currently no commercial vaccines or preventive treatments available for humans. Health officials warn that vigilance is required as Culex mosquitoes remain active until November.