West Nile virus has been detected in 12 European countries through locally acquired infections this year, up from nine at the same point last year, prompting the EU’s health agency to call for stronger mosquito-control measures.
The mosquito-borne disease can produce flu-like symptoms, but severe infections may lead to tremors, high fever, coma and encephalitis — a potentially fatal inflammation and swelling of brain tissue. Meningitis is another possible complication.
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According to the WHO, no vaccine for use in humans has been approved, and there is no specific treatment for the virus.
Medical care focuses on easing symptoms, while patients with serious infections may require supportive treatment in hospital.
Italy recorded the most cases, with 311, followed by Greece with 157. Across Europe, 21 regions reported West Nile virus infections for the first time.
That marks a sharp increase from the same period in August 2025, when 67 regions in nine European countries had reported cases.
“The expansion of West Nile virus transmission as well as the spread of invasive mosquito species demonstrate why Europe needs to strengthen its mosquito-control capacity,” ECDC executive Celine Gossner said in a statement.
“For effective mosquito control, we need close cooperation in Europe and an integrated approach that brings together mosquito monitoring, community engagement, and targeted mosquito control solutions that take environmental impact into account.”
Most human infections in Europe occur during the mosquito season, which typically stretches from late spring through autumn. Transmission generally reaches its highest level between July and September.
Culex mosquitoes, the principal carriers of West Nile virus, are already widespread across Europe. But the Asian tiger mosquito, or Aedes albopictus — which can spread dengue and chikungunya — is now established in 16 European countries, twice as many as 12 years ago, the ECDC said.
