An extremely painful tropical disease called chikungunya can now be transmitted by mosquitoes across much of Europe, a study has shown, the British newspaper The Guardian reports today.
Higher temperatures due to the climate crisis mean infections are now possible for more than six months a year in Spain, Greece and other southern European countries, and for two months a year in south-east England. Continuing global warming means it is only a matter of time before the disease spreads further north, scientists said.
The analysis is the first to fully assess the impact of temperature on the incubation time of the virus in the Asian tiger mosquito, which has invaded Europe in recent decades. The study found that the minimum temperature at which infections can occur is 2,5 degrees Celsius lower than in previous, less reliable estimates, a "quite shocking" difference, the researchers said.
Chikungunya virus was first discovered in 1952 in Tanzania and was confined to tropical areas, where millions of infections are recorded annually. The disease causes severe and long-lasting joint pain, which is extremely debilitating and can be fatal in young children and the elderly.
A small number of cases have been reported in recent years in more than a dozen European countries, but in 2025, France and Italy were hit by major epidemics with hundreds of cases.
Sandip Tegar, from the UK Centre for Ecology and Hydrology (UKCEH) and lead author of the study, said: "The rate of global warming in Europe is about twice the rate of global warming at the global level, and the lower temperature limit for the spread of the virus is very important, so our new estimates are quite shocking. The spread of the disease northwards is only a matter of time."
Dr Stephen White, also from UKCEH, said: "Twenty years ago, if you had said we were going to have chikungunya and dengue in Europe, everyone would have said you were crazy: these are tropical diseases. Now everything has changed. It's because of this invasive mosquito and climate change - it's really that simple. We're seeing rapid change and that's what's worrying. Until last year, France had recorded around thirty cases of chikungunya over the last decade or so. Last year they had over 800."
The virus was brought by travelers from French overseas territories in tropical regions, where there have been outbreaks, including Reunion.
The Asian tiger mosquito (Aedes albopictus), which bites during the day, is moving north across Europe as temperatures rise. It has been discovered in the United Kingdom but has not yet become established. There are expensive vaccines against chikungunya, but the best protection is to avoid being bitten.
Dr Diana Rojas Alvarez, who leads the World Health Organization's team on viruses transmitted by insect and tick bites, said: "This study is important because it suggests that transmission (in Europe) could become even more pronounced over time."
She added that chikungunya can be devastating, with up to 40 percent of people still having arthritis or very severe pain after five years.
"Climate has a huge impact on this, but Europe still has a chance to stop these mosquitoes from spreading further," she said. Educating the community about removing stagnant water where mosquitoes breed is one important tool, while wearing long, light-colored clothing and using repellents help prevent bites. Health authorities also need to set up surveillance systems, she said.
When a mosquito bites an infected person, the chikungunya virus enters their digestive system. Then, after an incubation period, the virus is in the mosquito's saliva, meaning it can infect the next person it bites. However, if that incubation period is longer than the mosquito's lifespan, the virus cannot spread.
The study, published in the Journal of the Royal Society Interface, used data from 49 previous studies of chikungunya virus in tiger mosquitoes to determine, for the first time, the incubation time across a range of temperatures.
The study found that the threshold temperature for transmission is 13–14°C, meaning that infections could occur for more than six months a year in Spain, Portugal, Italy and Greece, and three to five months a year in Belgium, France, Germany, Switzerland and a dozen other European countries. The minimum temperature was previously estimated at 16–18°C, meaning that there is a risk of chikungunya outbreaks over a wider area and for longer periods than previously thought.
The new research provides significantly more detailed information about areas at risk.
"Identifying specific locations and months of possible transmission will allow local authorities to decide when and where to take measures," Tegar said.
Outbreaks in Europe are triggered by infected travelers returning from tropical areas who are bitten by local tiger mosquitoes, which then spread the disease. Until now, cold European winters have stopped tiger mosquito activity and acted as a kind of barrier, preventing the disease from being transmitted from one year to the next.
However, scientists are beginning to record year-round activity of the tiger mosquito in southern Europe, meaning chikungunya outbreaks are likely to intensify as the continent warms.
The UKCEH team is investigating this question. "Our intuition is that we're going to have much larger outbreaks because you no longer have this natural barrier," White said.
There have not yet been any cases of local transmission of chikungunya in the United Kingdom, but a record number of 73 cases were registered between January and June 2025 among people who contracted the virus abroad, almost three times more than in the same period in 2024.
White said: "It is important to continue measures to prevent the tiger mosquito from becoming established in the (UK) as this highly invasive species is capable of transmitting several infections that can cause serious health conditions, including chikungunya, dengue and Zika viruses."
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