Italian health authorities have recorded more than 650 confirmed West Nile virus infections so far in 2026, roughly half of all cases reported across Europe this year, as the mosquito-borne illness spreads into provinces that had previously seen little or no transmission.
The virus, considered endemic in Italy since 2020, has been detected in 75 provinces across 19 regions, from Piedmont in the north to Sicily and Sardinia in the south. Of this year's confirmed cases, 269 involved the more severe neuro-invasive form of the disease, while 70 were asymptomatic infections identified through blood-donor screening and 179 presented as milder fever. Twenty-six deaths have been reported.
About 80% of people infected with West Nile virus show no symptoms at all, and most who do become ill recover within days to weeks. But severe neurological complications, such as encephalitis or meningitis, occur disproportionately among older adults and people with weakened immune systems, and can be fatal.
A Longer Season, a Wider Map
Researchers point to climate as the common thread behind the virus's spread. Antonino Bella, a researcher at Italy's National Institute of Health, said higher temperatures linked to climate change help mosquitoes reproduce faster and extend the transmission season, sometimes pushing detectable cases into November in a country where the season once reliably ended by early autumn.
A warming climate means that we have a longer mosquito season.
Marc-Alain Widdowson, World Health Organization Europe
The pattern is not confined to Italy. The Netherlands has logged more than two dozen West Nile cases in 2026, including several deaths, the country's first cases since 2020, a sign the virus's range is creeping northward across the continent. Public health agencies in Belgium have begun studying Italy's surveillance network as a model for detecting the virus earlier in newly affected regions.
Italian officials say there is no vaccine for human use, and prevention still relies on reducing mosquito breeding sites, using repellents and screening blood donations. With warm weather persisting into late September this year, regional health departments have extended mosquito-control spraying programs beyond their usual autumn cutoff dates.
The World Health Organization's European office has flagged West Nile virus as one of several mosquito- and tick-borne diseases it expects to expand across the continent as average temperatures rise, alongside dengue and chikungunya, both of which have caused small local outbreaks in southern Europe in recent years. Widdowson said WHO Europe is working with national health agencies to standardize surveillance so that new clusters are identified earlier, before the neuro-invasive form of the disease has a chance to spread within a region.
