2023-08-04 08:15:00
NEWS IN A NUTSHELL. A case of this virus transmitted by the mosquito has just been spotted in Bordeaux, a first for the south-west of France. Focus on its origins and symptoms.
By Remi Kumar
Published on
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Por the first time in France, a case of West Nile virus (WNV) has been detected outside the Mediterranean rim, in Bordeaux. In the past, it has always been reported in the Occitanie and Provence-Alpes-Côte d’Azur regions. Its appearance outside the usual areas testifies to its extension over the territory.
His origins
This virus was isolated for the first time in 1937 in Uganda (East Africa), west of the White Nile, a tributary of the Nile. In France, its first appearance was in the Camargue, in 1964. It was introduced to Europe by migratory birds from Africa and is found mainly in southern Europe. Since 2010, its circulation has been on the rise on the continent. In autumn 2022, cases were identified in horses in New Aquitaine, which may explain its recent presence in the region.
The mosquito as an intermediary
WNV is an arbovirus transmitted by mosquitoes. Originally a bird virus, but it spread to mosquitoes that feed on infected specimens. Humans and other vertebrate species can also be infected, but only through mosquito bites. These are the so-called Culex mosquitoes, the most common in mainland France. This insect acts as the only intermediary between humans and birds: the virus cannot be transmitted following direct contact between humans and an infected bird. Humans are “accidental hosts”. Its transmission is seasonal, it depends on the periods of mosquito activity. In metropolitan France, it extends from June to the end of November.
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80% asymptomatic
The virus has an incubation period of two to fourteen days. Of all people infected with the virus, nearly 80% remain asymptomatic. The remaining 20% can develop what are called “flu-like” symptoms, that is to say symptoms typical of a flu-like state without actually having it. These symptoms can be fever, joint pain or headache.
The virus poses a risk when a severe form is contracted; it can then lead to neurological damage (meningitis, encephalitis, etc.). The elderly are more prone to these advanced forms, which can cause sequelae or even death for the most fragile cases. Nevertheless, less than one person in a hundred contracts a severe form.
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