Italy has recorded more than 650 human cases of West Nile virus so far this year, accounting for roughly half of every case reported across Europe, and 17 people have died. The virus, transmitted by mosquitoes that pick it up from infected birds, has been confirmed circulating in 47 provinces spread across 12 Italian regions, stretching from Piedmont and Lombardy in the north down through Lazio, Campania, Sicily and Sardinia.
West Nile has been considered endemic in Italy since 2020, the year cases began to surge, and it now returns predictably every summer and into early fall rather than showing up as an occasional outbreak. Antonino Bella, a researcher at Italy's National Institute of Health, points to a straightforward mechanism behind the trend, higher temperatures tied to climate change let mosquitoes reproduce faster and extend the season during which an infected mosquito has time to pass the virus on to a person.
Italy is not alone in feeling that shift. The Netherlands has reported more than two dozen West Nile cases this year, its first since 2020, along with several deaths, evidence that the virus's range in Europe is not shrinking back to southern countries once the weather cools but expanding into places that treated it as a rare import until recently.
The broader mosquito picture backs that up. A decade ago, the Aedes albopictus mosquito, the Asian tiger mosquito capable of spreading multiple viruses, was established in 8 European countries across 114 regions. This year it is established in 13 countries and 337 regions, nearly tripling its footprint in ten years. Aedes aegypti, a species that can carry dengue, yellow fever, chikungunya, zika and West Nile, has been present in Cyprus since 2022 and researchers expect it to keep expanding into new parts of the continent.
None of this points to a single dramatic event Italy can respond to and close. It describes a slow widening of the map, more provinces added most years, more countries reporting cases that once looked like anomalies, and a mosquito season that keeps starting earlier and ending later as the climate warms underneath it. Public health officials can track the spread and count the cases. What they cannot yet do is make the season shorter.