As of August 21, 2026, 93 cases of West Nile fever had been confirmed in horses across France, with the majority—53 cases—found in the Occitanie region and 33 in Provence-Alpes-Côte d'Azur. By September 2, 2026, the number of confirmed cases in Provence-Alpes-Côte d'Azur had risen to 69, with the Bouches-du-Rhône department being the most affected. Emerging cases were also reported in the Var and Vaucluse departments. This number is higher than in the previous two years, and according to RESPE, a network that monitors equine diseases, the peak of the outbreak has not yet been reached. West Nile virus is primarily transmitted from infected birds to Culex mosquitoes, which then bite horses and humans, passing on the virus. In recent years, the virus has been expanding its range in France, moving northward. Cases have now been reported in Île-de-France and along the Atlantic coast. In 2022, the first horse infections were recorded on the Atlantic coast in Gironde, and in 2023, the virus was detected in both humans and horses outside the Mediterranean regions. In June 2026, the West Nile National Reference Laboratory in France confirmed six bird cases in four departments: Paris, Seine-et-Marne, Hauts-de-Seine, and Val-de-Marne. Mosquito traps in Val-de-Marne also detected the virus, showing its spread. According to Anses, the French Agency for Food, Environmental and Occupational Health Safety, over 250 bird species can carry the West Nile virus, including common birds like sparrows, crows, and hawks. The virus is mainly spread by Culex mosquitoes, which become infected after biting an infected bird. These mosquitoes can then transmit the virus to horses or humans. However, once the virus infects a mammal like a horse or human, it cannot be passed on to other mammals or mosquitoes. This means that infected horses cannot spread the virus to other horses, their owners, or the mosquitoes that bite them. A joint report by the European Food Safety Authority (EFSA) and the European Centre for Disease Prevention and Control (ECDC) noted that by early August 2026, there were 245 human cases of West Nile virus across Europe, with 17 cases in horses and 74 in birds. France has been one of the earliest countries affected this season, with the first cases in horses and birds reported on March 30, 2026—nearly a month earlier than usual. This early onset allowed the virus to spread more widely before the summer heat. To combat the spread of West Nile virus in horses, the only available medical tool is a vaccine. While it doesn't offer complete immunity, it can reduce the severity and duration of symptoms if a horse becomes infected. Health authorities recommend that horse owners consult a veterinarian early in the spring, before the mosquito season begins, rather than waiting for a peak in cases. Other preventive measures include bringing horses indoors at dusk, eliminating stagnant water where mosquitoes breed, and using mosquito nets in stables. These steps can't stop the virus in birds, but they can help break the transmission cycle at the final stage, preventing it from reaching horses.