Rome, Sept 19: Italian health authorities are reporting signs that rising temperatures and longer warm seasons are helping West Nile virus spread across a wider area and remain active for a longer period of the year.
More than 650 West Nile virus infections have been reported in Italy so far this year, accounting for roughly half of the cases recorded across Europe, according to Italian health authorities.
Antonino Bella, a researcher at Italy’s National Institute of Health (ISS), said warmer temperatures linked to climate change can support mosquito reproduction and extend the period during which the virus can be transmitted.
West Nile virus has been considered endemic in Italy since 2020, when infections began increasing significantly. Cases are now regularly reported during the summer and early autumn months.
Around 80 per cent of infected people show no symptoms, while most of those who develop symptoms experience a mild flu-like illness. A small proportion can develop severe neurological complications, particularly older people and those with underlying health conditions.
Experts said the number of infections recorded this year remains broadly comparable with recent seasons. However, warmer conditions can extend the transmission period, in some cases until November, while infections are increasingly being detected in areas that previously reported few or no cases.
Italy’s experience is also attracting attention from countries farther north in Europe. A Belgian research team visited the ISS earlier this year to study Italy’s surveillance and research systems after Belgium and other countries recorded cases.
The Netherlands has reported more than two dozen West Nile cases this year, along with several deaths, according to its public health institute.
Marc-Alain Widdowson, who heads the Pandemic Threats, Communicable Diseases and Antimicrobial Resistance Division at the World Health Organization’s Europe office, said warmer conditions can lengthen the mosquito season and create more favourable conditions for virus transmission.
However, experts caution that climate change is not the only factor involved. Changes in land use, biodiversity loss and mosquito populations can also influence the spread of the virus.
Italy’s extensive surveillance network, which monitors mosquitoes, birds, blood donors and human infections, also contributes to the country detecting a relatively high number of cases.
The European Centre for Disease Prevention and Control (ECDC) has warned that Europe’s warming trend, combined with more frequent heatwaves and flooding and longer, warmer summers, is creating increasingly favourable conditions for mosquito species capable of transmitting diseases.
The Aedes aegypti mosquito, which can transmit diseases including dengue, yellow fever, chikungunya, Zika and West Nile virus, has been established in Cyprus since 2022 and could potentially expand into other parts of Europe.
Meanwhile, Aedes albopictus, commonly known as the Asian tiger mosquito, has expanded significantly across the continent. According to the ECDC, it was established in eight European countries and 114 regions a decade ago. This year, it has been reported as established in 13 countries and 337 regions.
