Chikungunya Virus Transmission Expands Across Europe Due to Climate Change
An intensely painful tropical disease known as chikungunya can now be transmitted by mosquitoes across most of Europe, according to a recent study.
Rising temperatures linked to the climate crisis have extended the period during which infections are possible to over six months annually in countries such as Spain, Greece, and other southern European nations, and to about two months per year in south-east England. Scientists warn that ongoing global warming will likely cause the disease to spread further north in the near future.
The study represents the first comprehensive assessment of how temperature affects the incubation period of the chikungunya virus within the Asian tiger mosquito, an invasive species that has spread across Europe in recent decades. Researchers discovered that the minimum temperature at which infections can occur is 2.5°C lower than previous, less precise estimates, a difference they described as "quite shocking."
Chikungunya virus was initially identified in 1952 in Tanzania and was historically confined to tropical regions, where millions of cases occur annually. The disease causes severe and prolonged joint pain, which can be extremely debilitating and may be fatal in young children and older adults.
Although a small number of cases have been reported in over ten European countries in recent years, large-scale outbreaks are anticipated by 2025.
Expert Insights on Disease Expansion and Climate Impact
Sandeep Tegar, at the UK Centre for Ecology and Hydrology (UKCEH) and lead author of the study, said: "The rate of global warming in Europe is approximately double the rate of global warming at global scale and the lower temperature limit for virus spread matters a lot, so our new estimates are quite shocking. The northward expansion of the disease is just a matter of time."
Dr Steven White, also at UKCEH, stated: "Twenty years ago, if you said we were going to have chikungunya and dengue in Europe, everybody would have said you were mad: these are tropical diseases. Now everything’s changed. This is down to this invasive mosquito and climate change – it really is as simple as that. “We’re seeing rapid change and that’s the worry. Up until last year, France had recorded 30-odd cases of chikungunya over the last 10 years or so. Last year, they had over 800."
The virus was introduced by travelers from French overseas territories in the tropics experiencing outbreaks, including Réunion.
Asian Tiger Mosquito's Role and Geographic Spread
The Asian tiger mosquito (Aedes albopictus), which bites during the day, is advancing northwards across Europe as temperatures increase. While it has been detected in the UK, it has not yet established a permanent presence.
Although vaccines for chikungunya exist, they are costly, and the most effective protection remains avoiding mosquito bites.
Dr Diana Rojas Alvarez, who leads the World Health Organization’s team on viruses transmitted by insect and tick bites, commented: "This study is important because it indicates that transmission [in Europe] might become even more evident over time." She added that chikungunya can be devastating, with up to 40% of people still experiencing arthritis or very severe pain after five years.
"Climate has a huge impact on this, but Europe still has the chance to control these mosquitoes from spreading any further," she said. "Community education on removing the still water where mosquitoes breed is one important tool, while wearing long, light-coloured clothing and using repellent prevents bites. Health authorities also need to set up surveillance systems," she added.
Virus Transmission Mechanism and Study Details
When a mosquito bites an infected person, the chikungunya virus enters the mosquito's gut. After an incubation period, the virus reaches the mosquito’s saliva, enabling it to infect the next person it bites. However, if the incubation period exceeds the mosquito’s lifespan, the virus cannot be transmitted.
The study, published recently, analyzed data from 49 previous studies on chikungunya virus incubation in tiger mosquitoes to determine the incubation time across a full temperature range for the first time.
Findings revealed the transmission cut-off temperature is between 13°C and 14°C, meaning infections can occur for over six months annually in Spain, Portugal, Italy, and Greece, and for three to five months annually in Belgium, France, Germany, Switzerland, and about a dozen other European countries. Previous estimates placed the minimum temperature at 16°C to 18°C, indicating a greater risk of chikungunya outbreaks in more locations and for longer durations than previously understood.
The new data provides detailed information on specific areas at risk.
"Identifying specific locations and the months of possible transmission will enable local authorities to decide when and where to take action," Tegar explained.
Outbreak Dynamics and Future Risks
Outbreaks in Europe typically begin when infected travelers return from tropical regions and are bitten by local tiger mosquitoes, which then spread the virus. Historically, Europe's cold winters have halted tiger mosquito activity, acting as a natural barrier preventing the disease's persistence year-to-year.
However, scientists are now observing year-round tiger mosquito activity in southern Europe, suggesting chikungunya outbreaks may intensify as the continent warms. The UKCEH team is actively researching this phenomenon.
"Our intuition is that we’re going to get much bigger outbreaks because you don’t have this natural firebreak," White said.
Although no local chikungunya transmissions have yet been reported in the UK, there was a significant increase in imported cases between January and June 2025, nearly tripling compared to the same period in 2024.
White emphasized: "It is important there is continued action to try to prevent the tiger mosquito from establishing in [the UK] because this highly invasive species is capable of transmitting several infections that can cause serious health conditions including chikungunya, dengue and Zika viruses."
