Italian health officials have reported that rising temperatures and longer warm seasons are contributing to the spread of West Nile virus across a wider area and during more months of the year. This year, over 650 infections have been recorded in Italy, making up about half of all cases in Europe. Researchers attribute this increase to climate change, which allows mosquitoes to reproduce more effectively and extend the period during which they can transmit the virus. Antonino Bella, a researcher at Italy’s National Institute of Health, explained that warmer temperatures not only help mosquitoes thrive but also increase the likelihood of infected mosquitoes spreading the virus to humans. West Nile virus has been considered endemic in Italy since 2020, when cases began to rise significantly. It is now reported every summer and early fall. Most people infected with West Nile do not develop symptoms, and those who do typically experience mild, flu-like illness. Severe neurological complications are rare but more common among older adults and those with pre-existing health conditions. Although this year’s case numbers are in line with recent seasons, experts note that warmer temperatures can extend the transmission season into November, and areas that were once largely unaffected are now reporting infections. Italy’s experience with West Nile has drawn attention from other European countries, particularly those farther north. A Belgian research team visited Italy in May to study its surveillance and research system after the country began recording locally acquired cases. The Netherlands has also reported more than two dozen cases this year, the first since 2020, along with several deaths. Marc-Alain Widdowson, from the World Health Organization’s Europe office, said that warmer temperatures are likely to expand the virus’s replication period and mosquito season in more countries. He added that a warming climate allows mosquitoes to survive longer and increases the virus’s ability to persist. Experts highlight that Italy’s extensive monitoring system, which tracks mosquitoes, birds, blood donors, and human infections, contributes to the high number of detected cases. Widdowson also cited climate change, biodiversity loss, and land-use changes as factors increasing the virus’s activity. A longer mosquito season provides more opportunities for transmission, while declines in bird diversity may favor species that are efficient at carrying the virus. In June, the European Center for Disease Prevention and Control warned that Europe’s warming trend, including more frequent heatwaves and flooding, is creating favorable conditions for invasive mosquitoes such as Aedes albopictus and Aedes aegypti. These mosquitoes are known to transmit several diseases, including West Nile. Aedes aegypti has been established in Cyprus since 2022 and could spread further across Europe. The number of European countries affected by Aedes albopictus has also grown significantly in recent years.