Rising temperatures and longer warm seasons are helping mosquitoes spread West Nile virus across broader areas of Italy for more months of the year. Health authorities have reported more than 650 infections in Italy so far in 2026, accounting for roughly half of all cases recorded across Europe. Although West Nile virus has been considered endemic in Italy since 2020, medical researchers warn that warming weather is extending the transmission period deeper into the autumn.
Most people infected with West Nile virus develop no symptoms, while about 20 percent experience a mild flu-like illness. However, a small minority—mainly older adults and individuals with underlying health conditions—can suffer severe neurological complications. Antonino Bella, a researcher at Italy's National Institute of Health (ISS), explained that higher temperatures accelerate mosquito reproduction and allow transmission to continue as late as November, increasing the risk of virus spread to humans.
Italy's experience is attracting close attention from northern European countries facing similar threats. The Netherlands reported more than two dozen West Nile cases and several deaths this year, marking its first infections since 2020, while a Belgian research team visited the ISS in May to inspect Italy's surveillance system. Marc-Alain Widdowson, a pandemic threats official at the World Health Organization's Europe office, noted that while climate change is not the only factor, warmer weather clearly extends the period in which both mosquitoes and the virus can survive and replicate.
Experts emphasize that environmental shifts beyond temperature are also driving increased viral activity. Declines in bird diversity can favor species that act as efficient reservoirs for the virus, while changes in land use alter local habitats. Additionally, the European Centre for Disease Prevention and Control has warned that longer, warmer summers create favorable conditions for invasive mosquito species, expanding the geographical reach of insect-borne illnesses across the continent.