Italian health officials warn that warming conditions now fuel West Nile virus transmission across more of the country for longer stretches each year. More than half of Europe’s recorded infections in 2026 trace back to Italy.
Roughly 650 cases have surfaced nationwide this season, according to local authorities. That figure mirrors patterns from recent years, but the geography tells a different story.
Antonino Bella, a researcher at Italy’s National Institute of Health, pointed to hotter temperatures as the engine behind mosquito reproduction and longer active seasons. The virus has held endemic status in Italy since 2020, with infections reported every summer and early autumn.
Most people infected show no symptoms. About one in five develop mild flu-like illness. Serious neurological damage remains rare, concentrated among elderly patients and those with preexisting conditions.
Meanwhile, transmission now extends into November during warmer years, Bella noted. Regions once largely untouched have begun reporting cases, signaling the virus’s steady march across the country.
That shift has caught attention farther north. A Belgian research delegation visited the institute in May to study Italy’s surveillance approach after Belgium logged its first locally acquired cases. The Netherlands this year reported more than two dozen infections and several deaths, its first since 2020.
Marc-Alain Widdowson, who leads pandemic threats at the World Health Organization’s Europe office, said warming weather will expand the virus’s replication window in more countries. He cautioned against pinning everything on climate change, though he acknowledged longer mosquito seasons and better viral survival in heat play major roles.
Other factors compound the problem. Biodiversity loss and shifting land use alter bird populations, sometimes favoring species that serve as efficient virus reservoirs.
Italy’s dense monitoring network, which tracks mosquitoes, birds, blood donors and human cases, explains its high detection numbers. The European Centre for Disease Prevention and Control warned in June that hotter summers and more frequent floods create favorable conditions for invasive mosquito species.
Aedes albopictus, present in eight countries and 114 regions a decade ago, now spans 13 countries and 337 regions. Aedes aegypti has established itself in Cyprus since 2022 and could reach other nations. The trajectory points toward a permanent expansion of mosquito-borne disease risk across the continent.
