Mosquito season is currently underway in Europe, which means it’s also the time for mosquito-borne viruses.
So far this year, nearly 470 cases of West Nile virus, chikungunya, and dengue have been reported, according to the European Centre for Disease Prevention and Control (ECDC), which monitors cases across the EU and some neighboring countries.
These illnesses, typically transmitted through infected mosquito bites, are becoming increasingly prevalent in Europe, largely due to rising temperatures and greater travel linked to climate change.
Here’s a snapshot of what’s happening with these diseases and where cases have emerged this summer, up to mid-August.
West Nile virus
This year, West Nile virus infections have been confirmed in eight European countries: Italy (274 cases), Greece (35), Serbia (nine), Romania (six), France (four), Hungary (two), Spain (one), and Bulgaria (one).
These numbers comprise both confirmed and probable cases among individuals.
Most reported cases involve men aged 65 and older, with a significant number requiring hospitalization. Notably, at least 10 fatalities in Italy have been linked to West Nile virus in 2025.
Around 1 in 150 infected individuals may develop severe complications like encephalitis—an inflammation of the brain—or meningitis, which affects the protective membranes around the brain and spinal cord.
Such complications can be lethal, as per the World Health Organization (WHO).
Chikungunya
France has recorded 111 cases of chikungunya this summer, with a noticeable increase in recent weeks. This season has seen 22 clusters of chikungunya infections, of which 16 are still active.
Italy has reported seven cases as well.
While chikungunya is not endemic to the EU mainland, warmer summer weather facilitates the spread of the virus by mosquitoes. Most cases are usually reported in July or August, according to the ECDC.
There are two approved chikungunya vaccines in the EU, yet no specific treatments exist.
This virus can lead to various symptoms, including fever, nausea, headaches, fatigue, rashes, muscle aches, and joint pain, which can be severe and long-lasting. While extreme outcomes and fatalities are uncommon, infants and older adults face increased risks.
Dengue
France has seen 11 dengue cases this year, while Italy has reported four, and Portugal has had two cases.
Health authorities suspect that the Portuguese infections, which were identified in Madeira back in January, were acquired in the previous year.
The ECDC indicates that one species of mosquito responsible for transmitting dengue has established itself across much of Europe, while another is relatively common in regions like Madeira, Cyprus, and the Black Sea.
Globally, there are estimated to be 100 to 400 million dengue infections annually, according to the WHO.
While most dengue cases are mild or asymptomatic, the virus can result in fever, headaches, body aches, nausea, and rash. In severe instances, dengue can be life-threatening.
Currently, no specific medication is available for treating dengue, making bite prevention the most effective way to avoid infection.
