An autochthonous case of dengue, that is to say probably transmitted on the spot by a mosquito, has been identified for the first time in Île-de-France, announced Tuesday the health authorities, unprecedented for a region of metropolitan France so north.
The region's Regional Health Agency (ARS) confirmed in a statement that this was the "first indigenous case of dengue fever in Île-de-France". The case was identified in Limeil-Brévannes (Val-de-Marne), about 15 kilometres south-east of Paris.
An "indigenous case" means that the person has not recently travelled to parts of the world, such as the Caribbean, where this virus is widely circulated and transmitted from person to person by tiger mosquitoes. This means that the person was probably infected on the spot after being bitten by one of these mosquitoes, whose presence has been increasing for nearly 20 years in metropolitan France in a context facilitated by global warming.
Previous cases observed in the south of the country
This logically leads to an unprecedented increase in indigenous cases of dengue fever in mainland France: 66 in 2022 and already around thirty for the current year. Until now, these cases have been observed in southern regions, where the climate is a priori more favourable to the tiger mosquito. The case mentioned by the ARS Île-de-France is therefore the first in a region so far north.
In 2022, the epidemiological situation vis-à-vis dengue fever in metropolitan France was "exceptional", according to a report published this summer by Public Health France. Indigenous transmissions in the last year alone exceeded the total number of cases identified in 2010-2021 (66 cases, compared to 48).
Dengue fever is a viral disease that results in a high fever with, in rare cases, a progression to a more severe form causing bleeding. Deaths, however, are very rare – about 0.01% of all cases. In the French overseas territories, the West Indies have been in an epidemic phase since mid-August, and health authorities are monitoring risk profiles for severe forms, particularly patients with sickle cell anemia.