63 confirmed chikungunya cases recorded in south-east France as authorities fear epidemic

A sharp rise in imported chikungunya cases in the Auvergne-Rhône-Alpes region has prompted concern among health authorities, amid a broader uptick in mosquito-borne viral infections across mainland France.

As of May 27, 63 chikungunya cases have been recorded in the region for the month of May — up from just four during the whole of 2024 — alongside 47 cases of dengue. 

The departments of Rhône (20 cases) and Isère (18) are the most affected so far. 

The surge is linked to a major outbreak currently underway in France’s overseas department of La Réunion, according to the regional health authority (ARS).

The outbreak has killed 15 people on the island since the start of 2025, but none in mainland France.

All the cases recorded in the region are classified as imported - meaning they were contracted abroad - but officials warn that local transmission could follow if the tiger mosquito spreads the virus from infected individuals to others.

Chikungunya, dengue and Zika are all arboviral diseases transmitted by tiger mosquitoes. 

As of May 27, no home-grown cases have been detected this year in mainland France.

However, Santé publique France confirmed that between May 1 and May 27 - the period during which France’s reinforced seasonal mosquito surveillance is active - 341 imported chikungunya cases, 237 dengue cases, and one Zika case were reported nationally. 

The vast majority of these occurred in departments where the tiger mosquito is already established.

The insects, which first arrived in France in 2004, now have an established presence in 78 of 96 French departments (and all regions).

Tiger mosquitoes are identifiable by their black-and-white striped bodies (hence their ‘tiger’ name). Unlike ‘regular’ mosquitoes, they tend to be more active during the day, do not ‘buzz’, and are smaller (less than 0.5cm long).

National surveillance and rapid response

Health surveillance for these diseases is based on mandatory reporting throughout the year. 

Between January 1 and April 30, health authorities recorded 919 imported cases of chikungunya, 1,099 of dengue, and five of Zika across the country.

From May to November, when mosquito activity increases, this system is reinforced with targeted seasonal monitoring coordinated by Santé publique France in partnership with regional health agencies.

In the event of a reported case, rapid-response teams implement a strict protocol to prevent local transmission. 

This includes requiring infected individuals to remain indoors for several days, and carrying out insecticide spraying in a 150m radius around their homes and other places they may have visited — the maximum distance tiger mosquitoes typically travel.

Epidemic risk still considered low, but rising

Authorities stress that no local transmission has yet occurred on mainland France. 

However, two such cases were recorded in 2024, and the potential remains, particularly as tiger mosquitoes are now present across most of mainland France.

The Auvergne-Rhône-Alpes region is the second most affected in terms of arbovirus cases. Total infections have tripled in the past decade - from under 100 in 2014 to 269 in 2024.

To reduce the risk, health authorities are calling on residents to take preventive action. 

This includes removing standing water where mosquitoes can breed (e.g. flowerpots, buckets, clogged gutters), using repellents, and wearing long clothing during peak mosquito hours.