Nile virus: symptom, treatment, in France?

The West Nile Virus (or West Nile Virus) is an arbovirus mainly transmitted by mosquitoes. Most often asymptomatic, it can cause a sudden fever, sometimes associated with neurological complications. More details with Dr. Pascal Del Giudice, infectious disease specialist.

Definition: what is the Nile Virus?

West Nile Virus West Nile Virus) is a Arbovirus du genus Flavivirus (Flaviviridae family). It is considered today as the Flavivirus the most widespread after that of the dengue. It was first isolated in 1937 in the West Nile district of Uganda (Africa)hence its name, recalls Public Health France. It has historically been responsible for epidemics in Africa, the Middle East, West Asia and Europe. It appeared in North America for the first time in 1999 and in a few years it spread throughout the territory. In France, it is regularly detected around the Mediterranean. “It is transmitted to humans by mosquitoes, and more particularly speak mosquito Culex“, continues Dr. Pascal Del Giudice, infectiologist, and specialist in pathology. In Europe the virus was initially introduced by migratory birds from Africa. “The main hosts of the virus are birdsmammals (like man) are accidental hosts“.

What Symptoms Cause Nile Virus?

In 80% of cases, West Nile virus infection does not cause symptoms“, continues the specialist. The symptomatic forms of the disease are characterized by a fever brutal and important after 3 to 6 days incubation, which can be associated with a skin rash (discreet red patches). “The serious forms of the disease are rare (less than 1% of cases) and mainly affect adults and in particular the elderly. These are neurological disorders which manifest themselves by a meningitisencephalitis, meningoencephalitis… Moreover, in the south of France, where mosquitoes are very present, any syndrome with a neurological disorder and a high fever during the summer period, is the subject of a test for the detection of the Nile virus.“. The diagnosis can be confirmed by biological analyzes carried out in the blood and/or in the cerebrospinal fluid (CSF)through a lumbar puncture. “The horse is a species that is particularly susceptible to the West Nile virus. The viral infection is characterized by fever, encephalomyelitis and paralysis of the hind limbs, and causes a significant mortality rate. Cases of horses infected with the West Nile virus have been reported in several countries in Europe and the Mediterranean basin: in Egypt, in Italy (1998), in Israel (2000), in the United States (1999-2004), in France (in the Camargue in 2000 and in the Eastern Pyrenees in 2006), in Guadeloupe in 2002, and in Morocco in 2003, 2010, recalls thePastor Institute.

Those are the Migrator birds which act as reservoir animals for the West Nile virusexplains Dr. Del Giudice. Transmission of the virus to humans then occurs through bite of a mosquito, of the genus Culex. Mosquitoes become infected by feeding on infected birds“. Just like man, horses are also susceptible to infection.The only vector of contamination being the mosquito, the disease is present only in summer, between June and October“.

Is the Nile Virus present in France?

Since its first identification in East Africa, the virus has been identified on all continents, underlines the Pasteur Institute. Today it is endemic around the Mediterraneanin Central Europe and North America where it is responsible for fatal human cases as it has been observed in mainland Greece, southern Italy and the United States. The year 2018 was marked by the largest epidemic described, the number of cases recorded in Europe was higher than the sum of the previous 7 years, notes Public Health France. In 2019 and 2020 human cases were reported for the first time in Germany (2019 and 2020) and the Netherlands (2020). In France, the first human and equine cases have been diagnosed in the early 1960s. The virus reappeared in horses in the Camargue in 2000, and 7 human cases were recorded in 2003 in the Var. The virus travels with migratory birdscontinues our interlocutor. The number of cases therefore varies each year.

What is the mortality from West Nile Virus?

In cases of severe forms, where the disease presents as a severe neurological form (aseptic meningitis, meningoencephalitis, acute flaccid paralysis, Guillain Barré syndrome) mainly described in weakened subjects, the lethality was evaluated at 2% of infectionsreports the Ministry of Health.

What is the treatment for West Nile Virus?

“To date, there is no no specific antiviral treatment against the West Nile virus, concludes the doctor. Only the symptoms are treated: for example, by giving paracetamol to lower the fever“. For the horse, a equine vaccine is marketed. Prevention of West Nile virus infection is limited to protection measures against mosquitoes (individual and collective)

Thanks to Dr Pascal Del Giudice, head of the infectiology and dermatology department of the hospital center of Fréjus-Saint-Raphaël.

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