Dengue: a second indigenous case detected, already more than 1,600 cases in total in mainland France in 2025

The number of dengue cases continues to rise in metropolitan France. Two indigenous cases have even been detected.

It's not just chikungunya. Numerous cases of dengue fever have been detected in mainland France for several months. According to the latest report from Public Health France published on July 16, 2025, nearly 1,700 cases have been detected since the beginning of the year, including more than 580 between early May and mid-July alone. These cases were mainly imported from Guadeloupe, Martinique, and French Polynesia, since the virus is most prevalent in tropical areas. While the number of cases is worrying, it remains far from the record of 2024, with nearly 4,700 cases in mainland France.

Two indigenous cases of dengue fever, i.e., contracted within the territory, have been detected. The first was reported in early July, and the second on July 21. Both cases were detected in the Auvergne Rhône-Alpes region, specifically in Saint-Chamond, the Regional Health Agency stated in a press release.

How is dengue transmitted?

Dengue fever, like chikungunya, is transmitted by mosquitoes. The virus "is transmitted to humans through a bite by Aedes mosquitoes, primarily Aedes aegypti, but also sometimes the tiger mosquito ( Aedes albopictus ). When a mosquito feeds on the blood of an infected person, the mosquito can then infect other people," according to the Pasteur Institute . In some rare cases, dengue fever can also be transmitted from a pregnant woman to her baby or during a transplant or transfusion.

Unlike chikungunya , there are multiple strains of the virus, making it possible to be infected with dengue fever multiple times. A repeat infection even increases "the risk of developing severe dengue fever," according to the Pasteur Institute.

What are the symptoms of dengue fever?

In the majority of cases, dengue fever is asymptomatic, or manifests itself with mild symptoms. In infected individuals, after an average of 4 to 10 days, symptoms include high fever, headache, nausea and vomiting, and joint and muscle pain. A rash is also possible. "Symptoms persist for two to seven days, and the infected person's health generally improves," notes the Pasteur Institute.

But in rare cases, a severe, potentially fatal form of dengue fever occurs. It can cause severe abdominal pain, significant vomiting, hemorrhaging, extreme tachycardia, or even organ failure. There is no specific treatment for dengue fever, only symptomatic treatments.

How to protect yourself from dengue fever?

Unfortunately, there is no specific way to prevent dengue fever. No vaccine is available. "Individual prevention therefore relies primarily on means of protection against mosquito bites: repellent sprays or creams, coils, electric diffusers, long clothing, mosquito nets," reminds Public Health France .

Prevention is also collective, and is based on the fight against tiger mosquitoes, in particular by eliminating stagnant water points, where the insect's eggs can be laid.