Europe ramps up defences as invasive tiger mosquitoes advance, heightening tropical disease risks

In September, Portugal released 30,000 sterile male mosquitoes in a renewed effort to curb the burgeoning tiger mosquito population.

The Aedes albopictus, commonly known as the tiger mosquito, was first detected in Italy in the early 1990s via used‑tyre shipments and has since colonised France, Spain, Germany, Switzerland and many other European nations.

Alarmingly, the pathogens it transmits—dengue, chikungunya and Zika—are now appearing across the continent. Although infections remain scattered in most EU states, health authorities at both EU and national levels are striving to prevent these diseases from becoming endemic.

“The current trajectory does not bode well,” said Jan Semenza, an environmental epidemiologist, in an interview with Euronews. “If we do not act quickly to contain the spread, this problem will remain with us.”

Transmission occurs when mosquitoes bite infected people and subsequently bite others. Travellers returning from endemic regions can introduce the viruses into Europe, where local vectors may acquire and spread them.

“Many returnees bring the viruses back after holidaying in places such as Thailand or Brazil where these diseases are endemic,” Semenza explained. “A local mosquito can pick up the pathogen from an infected traveller, bite another person and trigger a locally‑driven outbreak.”

By the end of October 2026, Italy recorded 76 locally acquired dengue cases and France eight, roughly double the figure reported in 2025.

To address the surge, Portugal has launched a sterile‑male release programme. Males are irradiated to render them sterile, allowing them to mate with females without producing viable offspring.

“Our priority is to prevent Portugal from becoming an endemic country,” said André Peralta Santos, deputy chief of the Directorate‑General of Health.

Alternative control methods include the Wolbachia‑based approach successfully trialled in Brazil, where infection of mosquitoes with the bacterium blocks viral replication.

“‘You cannot autoclave the environment,’ Jan remarked. ‘Once the mosquito is established, it will persist; there is little that can be done to eradicate it.’”

Consequently, preparation is the only realistic course of action.

According to Semenza, this preparation entails “a combination of measures”, encompassing vector control, vaccination, antiviral therapy and especially community involvement.

Getting the citizens on board

“Citizens represent an under‑utilised resource,” observed Marion Koopmans, a virologist at Erasmus MC in the Netherlands. “In the realm of mosquito‑borne diseases, community‑generated information can be invaluable.”

Digital tools are proving effective. Applications like Mosquito Alert are deployed throughout Europe to monitor the northward expansion of tiger mosquitoes.

These citizen‑derived datasets are increasingly feeding formal surveillance systems, she added.

Crowd‑sourced reports enable authorities to map the mosquito’s spread. The species advances roughly 60 km northward annually, partly by hitchhiking in vehicles, while disease outbreaks move even faster—at about 120 km per year, Semenza noted.

While community monitoring is valuable, health authorities are also deploying diagnostics to detect the viruses before they spark local transmission.

International wastewater surveillance, supported by the EU’s Health Emergency Preparedness and Response Authority (HERA), is now operational.

“Through wastewater monitoring we can detect dengue circulation before patients seek care,” said Laurent Muschel, HERA’s director and deputy head. He described it as “a very powerful tool” and noted that HERA is investing heavily in it.

Surveillance extends to major European airports and to key international hubs in Singapore, Africa and Latin America.

“We are building a global early‑warning network to capture emerging signals worldwide,” Muschel explained.

“Early identification of cases is essential to curtail onward transmission. Prompt treatment and bite prevention are critical so that mosquitoes do not acquire and spread the virus further,” Semenza emphasised.

Surveillance is just one facet of the response. Vector control remains essential, and citizens can aid these efforts.

Control measures include installing insecticide‑treated screens, indoor spraying and removing any standing water that could serve as breeding sites.

Semenza cited community programmes in Nicaragua that teach residents to spot mosquito larvae in stagnant water and stress the need to keep containers clean.

“‘If you see standing water and what looks like a worm, it is actually a larva,’ Semenza explained. ‘It will develop into a mosquito and pose a public‑health risk.’”

Getting the tools ready

Even robust surveillance cannot stop every infection. As mosquito‑borne diseases become entrenched, health authorities must ensure clinicians can recognise them and that appropriate therapies are accessible.

“Patients may present with infections without recent travel,” Semenza noted. “How can physicians identify unfamiliar tropical disease symptoms when they have never encountered them before?”

To address this gap, HERA is allocating €10 million to develop advanced diagnostic tools.

“We lack suitable therapeutics for the emerging pathogens,” Muschel said, noting that HERA is funding research into antivirals and novel vaccines.

Existing dengue and chikungunya vaccines have limitations, Muschel observed. “We are working on improved formulations and may target vaccination at hotspots where vectors are active and transmission occurs.”

The reality is that mosquitoes are now established across several European regions, and authorities cannot wait for the diseases they carry to become endemic.

“‘The risk is already present,’ Semenza concluded. ‘Preparation is imperative.’”

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