As Europe warms, Italy sees West Nile virus spread

Francesco Severino, a senior researcher in medical entomology, places a net over a cage containing mosquitoes inside a laboratory at the Italian National Institute of Health in Rome, Friday, Sept. 18, 2026. Gregorio Borgia/AP hide caption

Italian health authorities see evidence that rising temperatures and longer warm seasons are helping mosquitoes spread West Nile virus across a wider area, during more months of the year.

More than 650 infections have been reported in Italy so far this year, accounting for roughly half of all cases recorded in Europe, according to local health authorities.

"Higher temperatures linked to climate change help mosquitoes reproduce and extend the transmission season, increasing the chances that infected mosquitoes will spread the virus to people," said Antonino Bella, researcher at Italy's National Institute of Health, or ISS.

West Nile has been considered endemic in Italy since 2020, when cases started to surge, and is now reported every summer and early fall. About 80% of infected people develop no symptoms, while most others experience a mild flu-like illness. Severe neurological complications occur in a small minority of cases, mainly among older adults and people with underlying health conditions.

Experts say this year's case numbers are broadly in line with recent seasons.

But warmer temperatures favor mosquito reproduction and can mean the transmission season sometimes lasts as late as November, Bella explained. Areas once largely unaffected are increasingly reporting infections, reflecting a gradual expansion of the virus across the country.

Italy's experience with the virus is drawing attention from European countries located farther north. A Belgian research team visited the ISS last May to study Italy's research and surveillance system after the country began recording locally acquired West Nile cases.