The tiger mosquito is now established and active in 81 departments of Mainland France. Its constant progression year after year is transforming a simple summer nuisance into a genuine public health issue. Beyond daily inconveniences, the tiger mosquito is a vector for viral diseases: dengue, chikungunya, and Zika. Since 2010, autochthonous transmission cases have been recorded every year in Mainland France, proving that the risk is now very real. Specifically, the mosquito can contract one of these diseases by biting an infected person returning from a trip to tropical areas where these viruses circulate. After 2 to 3 days, it can transmit the virus by biting another person, and it can do so throughout its life cycle (one month).

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Which diseases can the tiger mosquito transmit?

Beyond being a nuisance, the tiger mosquito can carry several viral diseases through its bites.

The main transmitted diseases are:

• Dengue
• Chikungunya
• Zika

These diseases are caused by viruses transmitted from person to person primarily through the bites of mosquitoes of the Aedes genus, to which the tiger mosquito belongs.

Dengue, chikungunya, Zika: what are the differences?

Dengue manifests as high fever, intense headaches, muscle and joint pain, sometimes accompanied by a skin rash. In rare cases, it can progress to a severe hemorrhagic form. Chikungunya is characterized by sudden fever and very intense joint pain, which can sometimes be disabling and persist for several months. Zika is distinguished by a skin rash, moderate fever, and conjunctivitis. Its main danger lies in the infection of pregnant women, which can lead to congenital malformations in the fetus.

Note: other mosquitoes of the Aedes genus can also transmit these viruses, but they are not currently present in Mainland France.

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Climate change: an accelerator of propagation

Global warming plays a major role in the expansion of the tiger mosquito and the increased risk of transmission in Mainland France. Milder winters favor better survival of eggs in diapause, while hotter and longer summers accelerate the insect’s development cycle. The tiger mosquito’s activity period is lengthening, as is the virus replication window inside the insect. Higher temperatures also make the mosquito contagious more quickly. Eventually, a large part of French territory could become favorable for the long-term establishment of the tiger mosquito and viral circulation.

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Risk zones: Overseas territories and travelers

The tropical zones where these viruses circulate are vast and include a majority of French overseas departments and territories. Mainland France is therefore exposed due to the large number of travelers who visit these regions every year.

The tiger mosquito, now established and active in 81 departments, can thus create an epidemiological bridge between endemic zones and Mainland France.

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Imported cases and autochthonous cases: what is the situation in Mainland France?

The link between these two types of cases is at the heart of epidemiological surveillance.

2025 Season: a record year

The year 2025 saw unprecedented viral circulation in Mainland France. According to data from Santé publique France, dozens of autochthonous transmission episodes were identified, totaling several hundred cases across the territory. The Provence-Alpes-Côte d’Azur region was particularly affected, recording over 450 autochthonous cases of chikungunya alone during the season. Dengue also circulated, with autochthonous clusters detected in southern France.

Regarding imported cases, the pressure was particularly strong due to active epidemics in French overseas territories: 932 imported cases of chikungunya (the majority from Reunion Island) and 775 imported cases of dengue (mainly from the French West Indies) were recorded. In total, more than 1,700 imported cases were identified during the surveillance period.

A case is considered autochthonous when a person contracts the disease without having stayed in an area where the virus is actively circulating in the two weeks preceding the symptoms. The infection therefore took place locally, through the bite of an infected tiger mosquito on mainland territory.

Imported cases involve people infected during a stay in an intertropical zone (Overseas territories, Asia, Africa, South America) who return to the mainland already infected. These cases are reported every year in the territory and constitute the main risk for the introduction of the virus.

These episodes show that the virus regularly arrives in the territory and that local transmission can occur when conditions are met: presence of the tiger mosquito, favorable temperature, and the arrival of an infected traveler.

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Symptoms: how to recognize these diseases?

Not all people infected by one of these viruses show symptoms (the proportion varies depending on the virus). However, when they do appear, signs may include:

• High fever (> 38.5°C) with sudden onset
• Muscle and/or joint pain (sometimes intense in chikungunya)
• Headaches
• Skin rash (as in dengue or Zika)
• Absence of respiratory signs or other signs of infection

If symptoms appear after returning from a trip to a risk zone, it is imperative to consult a doctor and mention the recent travel.

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How to protect yourself while traveling?

To limit the risk of infection and importation of the virus to the mainland, health authorities recommend:

• Using appropriate skin repellents
• Sleeping under a mosquito net
• Wearing long, loose-fitting clothing
• Eliminating standing water around your living area

Upon your return to France, if a fever occurs within 15 days, consult a doctor promptly.

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Conclusion: essential vigilance in the face of an expanding vector

The tiger mosquito is now established and active in 81 departments of Mainland France. This expansion, coupled with the influx of travelers from tropical zones, makes the risk of transmission more real than ever. Since 2010, the regular presence of autochthonous cases each year confirms that local transmission is no longer an exception. The year 2025 marked a turning point with an unprecedented level of viral circulation in Mainland France.

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Frequently Asked Questions (FAQ)

Does the tiger mosquito pose a health risk?

Yes, because it can transmit viruses such as dengue, chikungunya, and Zika. Not everyone who is bitten necessarily develops symptoms, but the risk of transmission exists, especially when the mosquito has previously bitten an infected traveler returning from a tropical zone. In the vast majority of cases, these diseases resolve spontaneously without lasting effects.

Can you catch the same disease multiple times?

Yes. For dengue, for example, there are four different serotypes. A first infection provides long-lasting immunity against that specific serotype, but not against the other three. A second infection by a different serotype can even increase the risk of severe forms.

Does a mosquito bite automatically mean infection? Should I consult a doctor?

No, a bite does not systematically lead to the transmission of a virus. However, if you develop symptoms such as sudden fever, joint pain, or a skin rash in the days following a bite (especially after returning from a trip to a tropical zone), consult a doctor and mention your stay. Avoid taking aspirin or ibuprofen without medical advice.

Can the tiger mosquito transmit Covid-19 or other diseases?

No. The tiger mosquito only transmits specific viruses: dengue, chikungunya, and Zika. It is not a vector for Covid-19, HIV, or the majority of respiratory viruses.