Painful tropical disease spreads in Europe as mosquito range expands

The tropical disease chikungunya, previously confined to warmer regions, can now be transmitted by mosquitoes across much of Europe, according to a new study published in Journal of the Royal Society Interface and monitored by Norway’s National Institute of Public Health (FHI).

The Asian tiger mosquito (Aedes albopictus), which carries the virus, has established itself in 16 European countries as of 2025, senior physician Elisabeth Astrup of the FHI told Dagbladet. Rising temperatures have enabled the species to spread, particularly in southern Europe.

“Travelers can become infected and bring the virus home,” Astrup said. “If the mosquito is present and conditions are right, it can transmit the infection to others, leading to small local outbreaks.”

Most infected individuals develop symptoms such as fever and joint pain, though some remain asymptomatic. While the disease typically resolves within 7–10 days, severe joint pain can persist for months or, in rare cases, years. Fatalities are uncommon, but the World Health Organization (WHO) reports that up to 40% of patients may still experience arthritis or severe pain five years after infection.

The FHI expects the tiger mosquito’s range to expand further but does not anticipate its establishment in Norway due to the climate. “Winter temperatures and average annual temperatures appear to be the main limiting factors for the tiger mosquito’s spread in Europe,” Astrup noted, adding that Norway’s conditions are currently unsuitable for either the virus or its vector.

The European Centre for Disease Prevention and Control (ECDC) monitors mosquito-borne infections during the summer season, with the FHI tracking developments. Last year, a major outbreak on the French island of La Réunion led to numerous imported cases in mainland France and Italy.

Study lead Sandeep Tegar of the UK Centre for Ecology and Hydrology told The Guardian that the disease’s northward spread is “only a matter of time.” However, Astrup emphasized that transmission is most efficient at 24–26°C, explaining why cases are concentrated in southern Europe.