In September, Portugal released 30,000 sterile male mosquitoes in a second attempt to curb the growing tiger mosquito population. By the end of October, the reported locally acquired dengue cases in Italy and France were roughly twice the 2025 total, while health authorities were working to ensure mosquito-borne diseases do not become endemic in Europe.
The irradiated males can mate with females but produce no offspring. EU and national health authorities are working to ensure diseases such as dengue, chikungunya and Zika do not become endemic in the bloc. By the end of October, Italy had reported 76 locally acquired dengue cases and France eight, roughly twice as many as in 2025. “The trajectory that we're on doesn't look good,” said Jan Semenza, an environmental epidemiologist. “This is a problem that will stay with us if we don't contain that as quickly as we can.”
The tiger mosquito, once found mainly in Southeast Asia, arrived in Italy in the 1990s through shipments of used tyres and has since spread to France, Spain, Germany, Switzerland and other European countries. It is moving around 60 kilometres further north each year, partly by hitching a ride in cars, while disease outbreaks are spreading even faster, at around 120 kilometres a year, according to Semenza. Infected travellers returning from tropical destinations can bring the viruses back to Europe, where local mosquitoes can pick them up and pass them on.
Eliminating the insects altogether is not realistic, Semenza said. “You cannot autoclave the environment,” he said. “Once the mosquito is established, the mosquito is here to stay; there's nothing you can do about it.” Authorities need to prepare with a combination of measures, including population control, vaccines and antivirals; surveillance is also part of the response.
Portugal's approach is one of several. Brazil has previously used mosquitoes infected with the Wolbachia bacterium, which blocked viruses from infecting them. The EU's Health Emergency Preparedness and Response Authority (HERA) is pouring €10 million into the development of new diagnostics and funding research into antivirals and new vaccines. "There are some vaccines for dengue and chikungunya; they are not perfect," said Laurent Muschel, director and deputy head of HERA. "We are trying to get better generations of vaccines and we might need to vaccinate a pocket of population where the mosquitoes are present and are transmitting the disease."
Digital tools are being used for surveillance. Wastewater monitoring, backed by HERA, can show whether dengue is spreading in Europe before a patient goes to the doctor, Muschel said, calling it a very powerful tool. Monitoring is taking place at major European airports as well as at international hubs in Singapore, Africa and Latin America. Citizen science apps such as Mosquito Alert are helping track whether tiger mosquitoes are entering new areas, which virologist Marion Koopmans of Erasmus Medical Centre said provides new data feeding surveillance. “We should not underestimate the power of citizens,” she said.
Community engagement matters too. Semenza pointed to Nicaragua, where communities are taught to recognise mosquito larvae in standing water and understand the importance of cleaning containers around their homes. "If you have standing water and you see a little worm in that water, that is not a worm, that's a larva, and that larva will hatch to become a mosquito and that is a problem for public health," he said.
André Peralta Santos, deputy chief of Portugal's Directorate-General of Health, said the fight is against becoming an endemic country. "The risk is here," Semenza said. "We need to prepare."
Analysis
Why This Matters
- Locally acquired dengue is no longer only a traveller's disease: Italy and France have reported roughly twice as many locally acquired cases as in 2025, and outbreaks are spreading about 120 kilometres a year.
- Europe's health systems are preparing for diseases they rarely saw before, with HERA investing in diagnostics, antivirals, vaccines and wastewater surveillance at airports.
- Officials say the window for containment is limited: once the tiger mosquito is established, it cannot be eliminated, so the response must focus on preparation and prevention.
Background
Dengue, chikungunya and Zika are viral diseases spread by the bites of infected mosquitoes, historically concentrated in tropical regions. The tiger mosquito, native to Southeast Asia, reached Italy in the 1990s through shipments of used tyres and has since spread through much of Europe, partly by hitching rides in cars. Heavy travel between Europe and tropical destinations allows returning travellers to bring the viruses home, where local mosquitoes can transmit them to others.
Key Perspectives
- Jan Semenza, environmental epidemiologist: says the current trajectory "doesn't look good", that once the mosquito is established it is here to stay, and that Europe needs a combination of population control, surveillance, vaccines and community engagement.
- André Peralta Santos, deputy chief of Portugal's Directorate-General of Health: says what Portugal is fighting against is becoming an endemic country.
- Marion Koopmans, virologist at Erasmus Medical Centre: says the power of citizens should not be underestimated, with their reports through apps providing new data for surveillance.
- Laurent Muschel, director and deputy head of HERA: calls wastewater surveillance "a very powerful tool", says Europe is missing the right medicines for these new diseases, and points out that existing dengue and chikungunya vaccines "are not perfect".
What to Watch
- Whether locally acquired dengue cases in Italy and France keep climbing into next year, which would signal the diseases are gaining a foothold.
- Whether HERA's wastewater surveillance network at European airports and global hubs detects local transmission before it reaches doctors.
- Whether next-generation dengue and chikungunya vaccines reach population-level use in areas where mosquitoes are already transmitting disease.
Checked
12 claims in this story checked against 1 source: 12 supported.
Show each claim
- SupportedSemenza said, “The trajectory that we're on doesn't look good.”Euronews: ““The trajectory that we're on doesn't look good,” Jan Semenza, an environmental epidemiologist, told Euronews.”
- SupportedSemenza said the problem would stay unless it was contained quickly.Euronews: ““This is a problem that will stay with us if we don't contain that as quickly as we can.””
- SupportedSemenza said, “You cannot autoclave the environment.”Euronews: ““You cannot autoclave the environment,” Jan said.”
- SupportedThe headline says Portugal released sterile mosquitoes as Europe's dengue threat spreads north.Euronews: “In September, Portugal has released 30,000 sterile male mosquitoes in a second attempt to curb the growing tiger mosquito population. [...] The tiger mosquito is moving around 60 kilometres further north each year [...] Disease outbreaks are spreading even faster, at around 120 kilometres a year, according to Semenza.”
- SupportedBy the end of October, Italy and France had reported locally acquired dengue cases at roughly twice the 2025 total.Euronews: “By the end of October 2026, Italy had reported 76 locally acquired dengue cases and France eight. That’s roughly twice as many as in 2025.”
- SupportedPortugal released 30,000 sterile male mosquitoes in September in a second attempt to curb the growing tiger mosquito population.Euronews: “In September, Portugal has released 30,000 sterile male mosquitoes in a second attempt to curb the growing tiger mosquito population.”
- SupportedThe mosquitoes were sterilised through irradiation and could mate but produce no offspring.Euronews: “Portugal has opted to tackle the problem by releasing male mosquitoes that had been sterilised through irradiation, meaning they could mate with females but produce no offspring.”
- SupportedThe tiger mosquito is moving about 60 kilometres further north each year, partly by hitching rides in cars; disease outbreaks are spreading about 120 kilometres a year, according to Semenza.Euronews: “The tiger mosquito is moving around 60 kilometres further north each year, partly by hitching a ride in cars. Disease outbreaks are spreading even faster, at around 120 kilometres a year, according to Semenza.”
- SupportedHERA is putting €10 million into developing new diagnostics and funding research into antivirals and new vaccines.Euronews: “That’s why the EU's Health Emergency Preparedness and Response Authority (HERA) is pouring €10 million into the development of new diagnostics. [...] the agency was funding research into antivirals and new vaccines.”
- SupportedMuschel said wastewater surveillance can show whether dengue is spreading in Europe before a patient goes to the doctor, and called it a very powerful tool.Euronews: ““You can see if dengue is spreading in Europe through wastewater surveillance before the patient goes to the doctor,” Laurent Muschel [...] told Euronews, calling this “a very powerful tool””
- SupportedMonitoring is taking place at major European airports and international hubs in Singapore, Africa and Latin America.Euronews: “Monitoring is taking place at major European airports as well as at international hubs in Singapore, Africa and Latin America.”
- SupportedSemenza said, “The risk is here,” and, “We need to prepare.”Euronews: ““The risk is here,” Semenza said. “We need to prepare.””
