Portugal Releases Sterile Mosquitoes to Curb Dengue Risk
Portugal released 30,000 sterilised male Asian tiger mosquitoes in Lisbon as Italy and France reported rising locally acquired dengue cases.
Updated on Nov. 4, 2026 in Diseases — General
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Portugal released 30,000 sterilised male Asian tiger mosquitoes in Lisbon in September 2026, aiming to reduce the population of an invasive species that can transmit dengue, chikungunya and Zika. The release comes as Italy and France reported locally acquired dengue cases by the end of October 2026.
Why it matters
Rising dengue cases and warmer temperatures are prompting European authorities to rethink how they prepare for tropical diseases. Infected travellers returning from tropical regions can introduce viruses that local mosquitoes then transmit.
Italy reported 76 locally acquired dengue cases and France reported eight by the end of October 2026, roughly double 2025 levels. Experts fear sporadic outbreaks could eventually become sustained transmission, and the effect of the Lisbon release on those numbers has not yet been measured.
The players
Health Emergency Preparedness and Response Authority (HERA)
The European Union's health emergency body, which is investing €10 million in new diagnostics for tropical diseases.
The details
Male mosquitoes were sterilised through irradiation before release, and they can mate with wild females, which then produce no offspring. The Asian tiger mosquito arrived in Italy in the 1990s and has since spread across much of southern Europe; this is the second time Portugal has used the sterile mosquito technique.
Timeline
Since the 1990s: The Asian tiger mosquito arrived in Italy.
September 2026: Portugal released 30,000 sterilised mosquitoes in Lisbon.
End of October 2026: Italy and France reported locally acquired dengue cases.
Roadmap
The Asian tiger mosquito is moving about 60 kilometres a year further north, and outbreaks are moving about 120 kilometres a year, so the Lisbon release and the Italian and French cases fit a documented northward trend. That trend places tropical disease transmission increasingly within reach of southern European populations.
Travellers returning from tropical regions can carry viruses that local mosquitoes then transmit, so awareness of symptoms after travel matters. Residents in affected parts of southern Europe may face more mosquito-borne illness as the species spreads north.
The takeaway
Mosquito-borne diseases once confined to the tropics are now appearing in southern Europe as the Asian tiger mosquito spreads north. Staying alert to symptoms after travel and supporting diagnostic investment are practical steps while control methods are tested.
Further reading
For more on how these infections are tracked and treated, see Diseases — General.
Source note: This article includes information reported by Euronews English.
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