This summer, West Nile virus has continued to spread across Europe, with cases reported in 16 countries and health authorities urging people to take preventive measures against mosquito bites. Six countries have reported particularly high numbers of cases over the past month, including several deaths.

France has been particularly affected. As autumn begins, the country is reporting record levels of West Nile virus infections in both humans and horses. According to data published by Santé publique France on 21 September 2026, 117 locally acquired human cases had been reported, already far exceeding the 62 cases recorded throughout 2025, itself a record year, when five deaths were reported for the first time in France.

More than 250 equine cases have also been reported in 2026, more than twice the previous record. The situation is not limited to France. More than 1,500 West Nile virus cases have been identified across Europe so far this year, with almost 80 deaths reported. Italy and Greece are currently the most affected countries, together accounting for more than half of the cases recorded at the beginning of September.

Île-de-France: a new area of virus activity

West Nile virus, traditionally associated with southern Europe and the Mediterranean, is expanding into new areas across the continent. In France, 16 departments have reported cases this year, including several reporting infections for the first time, such as Aude, Seine-et-Marne, Drôme, Rhône and Isère.

PACA remains the most affected region, with 39 human cases. However, the virus is also spreading further north and west, with new infections reported in Nouvelle-Aquitaine and local transmission continuing in Île-de-France, where cases have now been detected in five departments. The recurrence of cases in regions that have only recently been affected raises the possibility that West Nile virus is becoming established in new parts of France. The transmission season is also not necessarily over: infections can occur as late as November, while current weather conditions remain favourable for mosquito activity.