Due to the spread of tiger mosquitoes, France is now reporting rising numbers of cases of what were previously considered to be ‘tropical’ diseases such as chikungunya, Zika, dengue fever and West Nile virus.
It’s still true that the majority of cases of chikungunya, Zika, dengue and West Nile fever in France occur in people who have recently been in an area where those illnesses are endemic, such as Asia, the Caribbean or the Pacific Islands.
But due to the growing presence of tiger mosquitoes in France – which can spread these illnesses – there are a rising number of cases reported among people who have not left France.
These ‘cas autochtones’ (locally-transmitted cases) are also no longer confined to France’s Mediterranean coast and have been reported in northern and central France.
READ ALSO: How to protect yourself from mosquito-borne illnesses in France
The most recent bulletin from Santé Publique France, dated August 12th, reports 115 locally-transmitted cases of chikungunya this year, 11 cases of dengue fever and 7 cases of West Nile virus.
In previous years, cases were reported only in the south of France, in the Provence-Alpes-Côte d’Azur, Occitanie and Auvergne-Rhône-Alpes regions and on the island of Corsica.
This year, for the first time, locally-transmitted cases were reported in the central and northern regions of Grand Est and Bourgogne-Franche-Comté, as well as Nouvelle-Aquitaine in south-west France.
By contrast, there were 914 cases of chikungunya reported among recently-arrived travellers, as well as 746 imported cases of dengue and 4 imported cases of Zika.
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The map below from Santé Publique France shows the communes which have reported locally transmitted cases of either chikungunya or dengue since the start of this year.
Map showing locally transmitted cases of chikungunya and dengue reported in 2025. Map: Sante Publique France
When it comes to West Nile fever, two regions have reported locally transmitted cases: two outbreaks in Provence-Alpes-Côte d’Azur total of five cases and one outbreak in the greater Paris Île de France region, comprising two cases.
The real number of cases is likely higher because in more than half of people these illnesses produce no symptoms. Among people who do experience symptoms, the illnesses are usually not severe, but can be serious in vulnerable groups such as the elderly, young children and people with pre-existing medical conditions. Zika can be dangerous for pregnant women.
Deaths from these illnesses are very rare among people who have access to good medical care.
They are spread through the bites of tiger mosquitoes – which, unlike other mosquito breeds, fly and bite in the day as well as at night. It’s therefore advised to wear mosquito repellent throughout the summer season.
You can find more details on how to protect yourself and spot the symptoms of these illnesses here.