An unprecedented year in 2025, underscoring the importance of individual and collective preventive measures

The year 2025 was marked by an unprecedented number of chikungunya cases recorded in mainland France, with 81 local transmission clusters and nearly 809 indigenous cases identified. This represents the highest number of cases and indigenous transmissions of chikungunya identified since the implementation of enhanced surveillance in 2006. Regarding imported cases in mainland France, their number is largely attributable to the epidemic that occurred in the Indian Ocean, particularly in Réunion.
Additionally, 30 autochthonous cases of dengue were identified in mainland France, and 60 confirmed cases of West Nile virus infection were recorded.

Finally, for the first time, certain regions reported locally acquired cases of chikungunya (Burgundy-Franche-Comté, Grand Est, and New Aquitaine) and West Nile virus (Ile-de-France, Auvergne-Rhône-Alpes, and Normandy) within their territories.

Healthcare professionals play an essential role in the surveillance of arboviruses in mainland France. This surveillance relies on the system for notifiable diseases (MSO) for imported or locally acquired cases documented through laboratory testing, for which the Cerfa forms have been digitized for the first time.

Preventive measures are all the more essential given that the tiger mosquito is now established in 83 metropolitan departments 

The tiger mosquito (Aedes albopictus), first detected in mainland France in 2004, continues to gain ground, increasing the risk of transmitting diseases that can sometimes be serious. As of January 1, 2026, it had colonized 83 of the 96 metropolitan departments. Active from May to November, this vector can transmit dengue, chikungunya, and Zika. In this context, increased public and healthcare professional engagement in individual prevention measures is essential to limit its spread. 

Prevention is everyone’s responsibility! 

In the face of the proliferation of mosquitoes and the associated health risks, everyone can take daily steps to protect themselves and limit their spread:

• removing standing water (pots, tarps, gutters, etc.) helps limit the development of mosquito larvae;
• to avoid bites, it is advisable to take simple precautions: wear protective clothing, use repellents, and install mosquito nets (especially on strollers, windows, and doors).

By 2026, the risk of importation and spread to mainland France will increase. These diseases are actively circulating internationally—in the Americas, Southeast Asia, Africa, and the Pacific—and outbreaks are currently affecting France’s overseas territories. Travelers heading to these areas are urged to exercise heightened vigilance. Indeed, a person infected while traveling in a high-risk area may, upon their return, transmit the virus to a mosquito, which in turn may infect others. These new locally acquired cases could thus trigger an epidemic in mainland France.

Get informed before you leave, protect yourself from bites during your stay and for up to three weeks after your return. See a doctor immediately if you experience symptoms (fever, pain, rashes), and be sure to mention your travel history.