Health authorities in Italy reported that rising temperatures and extended warm seasons have contributed to the spread of West Nile virus across broader geographic areas and for longer durations during the year. According to the Italian National Institute of Health (ISS), more than 650 infections have been documented in the country this year. This figure represents approximately half of all West Nile cases recorded across Europe during the current season.
The virus has been considered endemic in Italy since 2020 following a surge in cases. While experts noted that this year’s infection numbers are generally consistent with recent seasons, the transmission period has expanded. Antonino Bella, a researcher at the ISS, stated that warmer temperatures facilitate mosquito reproduction and can extend the transmission season as late as November.
In addition to the rise in Italian cases, the virus is appearing in other parts of Europe. The Netherlands reported more than two dozen cases this year, the first since 2020, including several deaths. The European Center for Disease Prevention and Control (ECDC) reported in June that a warming trend in Europe, characterized by more frequent heat waves and flooding, has created favorable conditions for invasive mosquito species like Aedes albopictus, which is now established in 13 countries compared to eight a decade ago.
The presence of these viruses creates additional requirements for national health systems and blood donation centers. Italy currently maintains an extensive monitoring network that tracks mosquitoes, birds, and blood donors to detect the virus early. Marc-Alain Widdowson of the World Health Organization’s Europe office noted that a warming climate, combined with changes in land use and a loss of biodiversity, allows vectors to survive longer and the virus to replicate more efficiently. This sets a precedent for northern European nations, such as Belgium, to adopt similar surveillance systems as the virus moves into previously unaffected regions.
What happens next depends on seasonal weather patterns and the further movement of invasive species like Aedes aegypti, which has been established in Cyprus since 2022. The ECDC continues to monitor the spread of Aedes albopictus, which has already expanded from 114 regions a decade ago to 337 regions this year. Health authorities in Italy and the Netherlands will continue tracking human infections and mosquito activity through the end of the transmission season, which can now last through November. No specific dates for new health mandates or vaccination programs were reported.