Portugal Faces High Risk of Chikungunya Transmission, Study Warns
A new study published in the journal of The Royal Society has classified Portugal as a high-risk area for Chikungunya virus transmission, revising downward the temperature threshold at which the mosquito-borne disease can spread and raising alarm...
A new study published in the journal of The Royal Society has classified Portugal as a high-risk area for Chikungunya virus transmission, revising downward the temperature threshold at which the mosquito-borne disease can spread and raising alarm about the potential for local outbreaks lasting half the year.
Researchers at the UK Centre for Ecology and Hydrology found that the Chikungunya virus can be transmitted at air temperatures as low as 13 to 14 degrees Celsius, significantly below the 16 to 18 degrees previously assumed. The finding means that in southern European countries, including Portugal, Spain, Italy, and Greece, conditions are suitable for transmission during approximately six months of the year.
The study mapped risk across the continent in three tiers. Portugal sits firmly in the highest category, alongside its Mediterranean neighbours. The risk gradient decreases as one moves north and northwest, but the researchers noted that roughly 50 percent of Europe's geographical area is now conducive to transmission during the peak summer months of July and August.
Chikungunya is a viral disease transmitted by infected Aedes mosquitoes, particularly the tiger mosquito (Aedes albopictus), which has been steadily expanding its range across Europe as temperatures rise. The disease causes severe joint pain, fever, and fatigue, with symptoms that can persist for weeks or months. While rarely fatal, it can be debilitating, and there is no specific antiviral treatment.
The warning comes against a backdrop of real-world precedent. In 2025, France and Italy reported record numbers of locally acquired Chikungunya cases, and the tiger mosquito has also been linked to rising dengue infections in those countries. Portugal has so far avoided significant local transmission, but the conditions are increasingly favourable.
Fernando Almeida, president of Portugal's Ricardo Jorge National Health Institute (INSA), stated in November 2025 that the country's Revive vector surveillance network, comprising around 350 specialists nationwide, is prepared to respond to mosquito-borne disease emergencies. The network monitors mosquito populations and can trigger targeted interventions when risk thresholds are crossed.
For residents and visitors, particularly those in southern and central Portugal where summer temperatures routinely exceed the transmission threshold, the practical implications are straightforward: mosquito prevention measures, including repellent use, eliminating standing water, and installing screens, become increasingly important as spring approaches. The Algarve, Alentejo, and Lisbon metropolitan area are likely to see the longest transmission windows.
Sandeep Tegar, the lead researcher, emphasised that the revised data should help local authorities make better decisions about when and where to deploy mosquito control resources. "The lower temperature limit we have identified will result in more areas, and more months of the year, potentially suitable for transmission," he said, adding that warmer conditions also accelerate viral replication within mosquitoes, compounding the risk.
