The Chikungunya virus, responsible for a debilitating tropical disease caused by the bite of infected mosquitoes, poses a “greater threat to health in Europe than previously thought, as it can be transmitted when air temperatures are as low as 13 degrees Celsius,” concluded the research published today in the scientific journal The Royal Society.

In practice, the new study found that the virus can be transmitted at temperatures as low as 13 to 14 degrees Celsius, contrary to previous research that indicated a minimum of 16 to 18 degrees Celsius, according to the independent research institute with about 600 researchers from various fields.

This means that there is a risk of local outbreaks of Chikungunya in more areas and for longer periods than previously thought, warned the researchers, who created a map for Europe with three levels of risk - high, moderate and low.

Portugal is classified as a high-risk area, along with countries such as Greece, Italy, Malta and Spain, with the study predicting that transmission could occur for around six months of the year.

The risk gradient is highest in southern Europe, decreasing as one moves north and north-west, the study concluded, warning that approximately 50% of Europe’s geographical area is now conducive to transmission during July and August.

In 2025, record numbers of local outbreaks of Chikungunya were reported in France and Italy, and the tiger mosquito (Aedes albopictus) has also been responsible for an increase in dengue cases in these countries in recent years.

Researchers warned that, as Europe rapidly warms due to climate change, the tiger mosquito is gradually expanding northwards across the continent.

“The lower temperature limit we have identified will result in more areas – and more months of the year – potentially suitable for transmission” of the virus, said Sandeep Tegar, a specialist at the UK research centre that led the study, pointing out that warmer weather also increases the rate of virus replication in an insect’s body, thus increasing the risk of transmission.

Reducing the risk

Identifying specific locations and months of possible transmission will allow local authorities to decide when and where to act to reduce the risk or scale of outbreaks, Sandeep Tegar added.

In November 2025, the president of the Ricardo Jorge National Health Institute (INSA), the institution that officially coordinates the Vector Surveillance Network, emphasised that Portugal is prepared to respond to any emergencies caused by mosquito- and tick-borne diseases.

Fernando Almeida told Lusa that Revive – Vector Surveillance Network has around 350 employees across the country, ensuring the early detection of vectors that transmit diseases such as Zika, Dengue and Chikungunya, at a time when the Aedes albopictus mosquito is already widespread throughout almost the entire country.

Revive’s 2024 report indicated that the mosquito species in question was detected, from 2017 onwards, in the North, the Algarve, the Alentejo and Lisbon, and in 2024 for the first time in the Centre, which points to a “situation of establishment and geographical dispersion” across various regions of the country.