For the first time, cases of Western Nile fever were identified in Ile-de-France. Alsace and Burgundy have also identified cases of Chikungunya.
From Nile to the Seine, in a few mosquito wing beats: several thousand kilometers from the banks of the river from which it takes its name, the Western Nile virus was detected in Ile-de-France for the first time. The Regional Health Agency (ARS) indicated in a statement published this Wednesday that it has identified in recent weeks two indigenous cases of this arbovirosis in Seine-Saint-Denis. “” These are the first identifications of local vector transmission of the West Nile virus in Île-de-France Comments the ARS.
Close to those of yellow fever, dengue, zika and Japanese encephalitis, the Western Nile virus is transmitted by the most common mosquito, the most common in mainland France. However, it cannot be transmitted from human to human, nor via a mosquito having bitten an infected person.
115 Autochtones de Chikungunya in 2025
It is indeed the birds that constitute the natural reservoir of the virus. If the disease was first mainly confined to Africa and the Middle East, it began to reach Europe in 2010. In France, the rare human and equine cases were currently confined to the south-east of France. Five indigenous cases have also been identified in the PACA region since the start of the year.
If affected people are asymptomatic in 80 % of cases, this virus can cause various symptoms such as fever, headache, asthenia or nausea. In rare cases (approximately 1 %), Western Nile fever can cause potentially fatal serious neurological disorders, people over the age of 60 are more at risk.
The appearance of this virus in such a northern region occurs in a context of a strong increase in the number of cases of indigenous arboviroses. According to the latest public health assessment France (SPF), published this Wednesday, 23 homes of Aboriginal contamination by Chikungunya, virus transmitted by the Tiger mosquito, have been identified since last May, combining 115 cases of Chikungunya, unheard of in metropolitan France. If the majority of cases were identified in the south-eastern France, contamination took place in Dijon and Alsace. The spread of the dengue virus, also transmitted by the tiger mosquito, is more modest: six epidemic foci have been identified, combining 11 Aboriginal cases, all in the south of France.
Soon epidemics of arboviroses in mainland France?
The proliferation at unpublished levels of chikungunya in mainland France is favored by the import of many cases (914 cases imported from the 1is May), especially from the meeting. The island was indeed struck last spring by a large epidemic, which will have touched more than 20 % of the population and caused the death of twenty people. But the fact that indigenous cases were, for the first time, identified in the north of the Loire, shows that the tiger mosquito, which appeared in our regions in 2004, gained ground thanks to global warming. Long confined to the south of France, it is now present in 81 metropolitan departments (only Brittany and Normandy are spared).
In view of this rampant proliferation of the Tiger mosquito, which concerns all of Europe and the acceleration of global warming, many experts believe that it is only a matter of time before the metropolis in turn knew important epidemics of chikungunya or dengue. In 2024, the health security agency (ANSES) said likely that an epidemic will occur in the next five years while in May, a study published in The Lancet estimated that the risk of epidemic in Europe was going to be multiplied by five by 2060.