A new study reveals that chikungunya, a painful tropical disease, can now be transmitted by mosquitoes across most of Europe, with experts predicting further northward expansion as global heating continues.
Climate Impact on Disease Spread
Higher temperatures, attributed to the climate crisis, enable infections for over six months annually in southern European countries like Spain and Greece, and for two months yearly in areas such as south-east England. Scientists predict further northward expansion as global heating continues.
Key Study Findings
The analysis is the first to fully assess how temperature affects the incubation time of the virus in the Asian tiger mosquito (Aedes albopictus), an invasive species in Europe. The study determined the minimum temperature for infections is 2.5°C lower than previous estimates, a difference described as "quite shocking" by researchers.
Chikungunya was first identified in Tanzania in 1952 and was historically limited to tropical regions, causing millions of infections annually. The disease causes severe and prolonged joint pain, which is debilitating and can be fatal in young children and older adults.
European Outbreaks and Expert Views
Small numbers of cases have been reported in over ten European countries in recent years, with large outbreaks of hundreds of cases occurring in France and Italy in 2025.
Sandeep Tegar, lead author from the UK Centre for Ecology and Hydrology (UKCEH), stated that Europe's rate of global warming is approximately double the global average, making the lower temperature limit for virus spread significant. He added, "The northward expansion of the disease is just a matter of time."
Dr. Steven White, also from UKCEH, noted the rapid change, saying that the presence of chikungunya and dengue in Europe was once considered unlikely. He attributed this to the invasive mosquito and climate change. France, for example, recorded over 800 cases last year, compared to around 30 cases over the preceding decade. These cases were introduced by travelers from tropical French overseas territories experiencing outbreaks.
Transmission Mechanism and Prevention
The Asian tiger mosquito, which bites during the day, is moving north across Europe as temperatures rise. It has been detected, but not yet established, in the UK. While costly vaccines exist, avoiding mosquito bites is the primary protection.
Dr. Diana Rojas Alvarez, who leads the World Health Organization's team on insect-transmitted viruses, stated that this study indicates transmission in Europe might become more evident over time. She noted chikungunya's severe impact, with up to 40% of individuals experiencing arthritis or severe pain after five years. She emphasized that Europe can still control mosquito spread through community education on removing stagnant water, wearing protective clothing, using repellent, and implementing surveillance systems.
When a mosquito bites an infected person, the chikungunya virus enters its gut. After an incubation period, the virus is present in the mosquito's saliva, allowing it to infect the next person it bites. Transmission requires the incubation period to be shorter than the mosquito's lifespan.
Revised Transmission Thresholds
Published in the Journal of Royal Society Interface, the study utilized data from 49 previous studies to determine the incubation time across various temperatures. It found the cut-off temperature for transmission is 13°C-14°C, significantly lower than the previous minimum estimate of 16°C-18°C.
This means infections can occur for over six months annually in Spain, Portugal, Italy, and Greece, and for three to five months in Belgium, France, Germany, Switzerland, and other European countries. This revised estimate suggests a greater risk of outbreaks in more areas and for longer durations than previously understood.
Localized Action and Future Risks
The new data provides detailed information on at-risk areas. Tegar stated, "Identifying specific locations and the months of possible transmission will enable local authorities to decide when and where to take action."
European outbreaks are typically initiated when infected travelers from tropical regions are bitten by local tiger mosquitoes, which then spread the disease. Historically, Europe's cold winters halted tiger mosquito activity, acting as a natural firebreak. However, scientists are now observing year-round tiger mosquito activity in southern Europe, suggesting chikungunya outbreaks may amplify as the continent warms. The UKCEH team is investigating this, with White anticipating "much bigger outbreaks because you don’t have this natural firebreak."
UK Situation and Broader Concerns
No local transmissions of chikungunya have been reported in the UK. However, 73 cases among individuals who contracted the virus abroad were recorded between January and June 2025, nearly three times higher than the same period in 2024.
White stressed the importance of continued action to prevent the tiger mosquito from establishing in the UK, as this invasive species can transmit several infections, including dengue and Zika viruses, which can cause serious health conditions.