West Nile virus reported in 12 European countries

Twelve European nations have documented locally-acquired cases of the West Nile virus in 2025, according to the EU health agency. Italy and Greece reported the highest numbers of infections -- 311 and 157 respectively. The mosquito-borne virus can trigger symptoms akin to flu, but in severe instances, it can lead to tremors, fever, comas, and encephalitis or meningitis.

As of now, the virus has been identified in 99 regions across the 12 affected countries. These countries include Albania, Austria, France, Germany, Greece, Italy, Kosovo, the Netherlands, North Macedonia, Romania, Serbia, and Spain. The ECDC reported that 21 regions had their initial cases in 2025, compared to 67 regions in nine European countries during the same period in 2025.

Celine Gossner, ECDC's head of food, water, vector-borne, and zoonotic diseases, emphasized the need for Europe to enhance its mosquito-control capabilities, citing the expansion of West Nile virus transmission and the spread of invasive mosquito species. She stressed the importance of close cooperation and an integrated approach to mosquito monitoring, community engagement, and targeted mosquito control solutions that consider environmental impact.

Most human infections occur during the mosquito season, typically spanning late spring to autumn, with peak transmission between July and September. There are no approved vaccines or specific treatments for the virus, and care primarily involves symptom management and supportive hospital treatment for severe cases. The mosquitoes that spread West Nile virus (Culex mosquitoes) are already widespread in Europe, but the Asian tiger mosquito (Aedes albopictus), capable of transmitting dengue and chikungunya viruses, has now established itself in 16 European countries, twice the number from a decade ago.