Rising temperatures and longer warm seasons are driving mosquitoes to spread West Nile virus across wider areas of Italy and deeper into the autumn months, according to Italian health authorities. More than 650 infections have been reported nationwide this year, accounting for roughly half of all cases recorded across Europe.
Italy’s Surging West Nile Cases and Climate Factors
Higher temperatures linked to climate change help mosquitoes reproduce and extend the transmission season, according to Antonino Bella, a researcher at Italy’s National Institute of Health, or ISS. This dynamic increases the chances that infected mosquitoes will spread the virus to people. West Nile has been considered endemic in Italy since 2020, when cases began to surge, and it 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. A small fraction of patients, primarily those with preexisting health issues or older adults, experience serious neurological complications. Experts note that this year’s case numbers are broadly in line with recent seasons, but warmer temperatures mean the transmission season sometimes lasts as late as November, Bella explained. Infections are being reported more frequently in regions that were previously largely unaffected, signaling a slow spread of the virus throughout the nation.
Broader European Impact and WHO Warnings
Italy’s experience with the virus is drawing attention from European countries located farther north. Researchers from Belgium traveled to the ISS to examine Italy’s surveillance and research framework following the emergence of locally acquired West Nile cases in the country. Meanwhile, the Netherlands reported more than two dozen West Nile cases this year—its first since 2020—along with several deaths, according to its public health institute.
Marc-Alain Widdowson, who leads the Pandemic Threats, Communicable Diseases, and AMR Division at the World Health Organization’s Europe office, stated that warming weather will undoubtedly expand the period of replication for the virus and the vector in more countries. He noted that while climate change is not the only factor, a warming climate means a longer mosquito season for vectors to survive, while warm temperatures also help the virus itself survive better. Widdowson also cited a warming climate, loss of biodiversity, and changes in land use as contributing trends. He added that a prolonged mosquito season provides more chances for transmission, while the loss of bird diversity might benefit species that serve as effective reservoirs for the virus.
ECDC Warnings on Invasive Mosquito Species
In June, the European Center for Disease Prevention and Control, or ECDC, warned that Europe’s warming trend—featuring more frequent heat waves and flooding, alongside longer and warmer summers—creates favorable conditions for invasive mosquito species such as Aedes albopictus and Aedes aegypti. Since 2022, Aedes aegypti—which is known to transmit zika, yellow fever, chikungunya, West Nile, and dengue viruses—has been established in Cyprus and could potentially migrate to other European nations.
Did you know? A decade ago, the Aedes albopictus mosquito was established in eight European countries across 114 regions. According to the ECDC, the mosquito is now established in 13 countries and 337 regions.
Specialists suggest that the high number of detected cases in Italy is partly due to the country’s comprehensive monitoring system, which keeps track of human infections, blood donors, birds, and mosquitoes.
Frequently Asked Questions
What causes the spread of West Nile virus in Europe?
According to health officials like Antonino Bella of the ISS and Marc-Alain Widdowson of the WHO, rising temperatures linked to climate change extend warm seasons, help mosquitoes reproduce, allow vectors and the virus to survive longer, and lengthen the transmission season.
How many West Nile cases has Italy reported?
Italy has reported more than 650 infections so far this year, which accounts for roughly half of all cases recorded across Europe, according to local health authorities.
What are the symptoms of West Nile virus?
About 80% of infected people develop no symptoms, while most others experience a mild flu-like illness. A small minority of cases, primarily among people with underlying health conditions and older adults, result in severe neurological complications.
Are other European countries affected?
Yes. The Netherlands reported more than two dozen cases and several deaths this year, marking its first cases since 2020. Additionally, a Belgian research team visited Italy to study its surveillance system after recording locally acquired cases.
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