Virus of the Western Nile

The virus of the Western Nile (in English: West Nile Virus ) is a Flaviviridae kind Flavivirus (which also includes/understands the virus of the Yellow fever, the virus of the Dengue, the virus of the Encéphalite of Saint Louis and the virus of the Encéphalite Japanese woman).

Its name comes from the district of West Nile in Uganda where it was insulated for the first time in 1937 at a woman suffering from strong a Fièvre. It then has been detected in men, birds and mosquitos in Egypt in the Années 1950, and has for summer found in the man or the animal in various countries.

Human cases of fever, related to the virus of the Western Nile, were reported in Africa, with the the Middle East, in India, Europe, and more recently on the American continent, where a first epidemic was declared in the town of New York in 1999.

Epidemiologic table

Mode of transmission

The Mosquito S, and in particular the Culex , are the principal vectors of the virus of the Western Nile, and all the factors supporting the pullulation of the mosquitos (abundant rains, irrigation, temperatures higher than the normal…) are likely to increase the incidence of the Fièvre related to this virus in the geographical sectors where it circulates.

The principal hosts are the Oiseau X, which they are wild or servants (Canard S, Pigeon S…), because they play a crucial role in the dissemination of this virus. The migratory birds allow in particular the passage of the virus of the Africa the moderate zones of Europe and Asia in spring. Once arrived, the local mosquitos infect themselves when they prick these birds for their meal of blood, disseminating on other healthy birds the virus and perpetuating the cycle mosquitos/birds essence with circulation of the virus.

Mammalian S (cattle, Dog S, cat S, horses, human…) as for them are regarded as accidental hosts of the virus.

Symptoms at the man

The symptoms of the infection by the virus of the Western Nile, are similar to those of the influenza, but the majority of people do not feel any of it. She is characterized by the occurred brutal one of an important fever after 3 to 6 days of incubation, accompanied by , cutaneous eruption and back, muscular pain, Toux, swelling headaches of the Ganglions of the neck, often nausea S, of abdominal pains, respiratory diarrheas and symptoms. In less than 15% of the cases, complications can occur such as Méningite S, Encéphalite S, Hépatite S, Pancréatite S or Myocardite S.

Generally the patient recovers spontaneously, sometimes with after-effects, but the disease can prove mortal, at the immunodéprimées elderly or in 3 to 15% of the cases.

Tracking and treatment

There exists a screening test, but there does not exist specific treatment, nor of vaccine against the virus of the Western Nile. The treatments suggested only aim at attenuating the symptoms of the disease.

Zones at the risk

In the moderated zones, the cases of Encéphalite S due to this virus generally occur at the end of the summer or at the beginning of the autumn. In the other hotter areas, the virus is likely to be transmitted throughout the year.

In the south of the France, first described human endémie took place in 1962 with 50 cases of encéphalites including 10 severe cases, and between 1975 and 1980, of new human cases were identified in the Corsica Camargue and .

Prevention

At the individual level, the traditional means of prevention against the Moustique S are effective: Insecticidal Mosquito net, , anti-mosquito cream. The wearing of covering clothing also protects.

It is recommended to avoid any contact with naked hands with dead animals.

The campaigns of Désinsectisation by air are the only means of eliminating the mosquitos and the larvae on large surfaces in the ponds and the marshes.

In 2003:

a research made with the the United States, on the gifts of 6,2 million blood donors made it possible to find 1.000 donors positive and two probable cases of transmission of encéphalite, dependant on this virus, by blood transfusion (0,00016%).
the same study made in the department of the VAr in France, allowed, on a panel test of 200 blood donors to highlight that two of them had been in contact with the virus (1%). Other donors having been with the contact with the virus were found in 2003 with the French West Indies, in Guyana and with the Réunion.

The Croix-Rouge Suisse also took precautionary measures: any person returning of the zones where the virus prevails, of which the the United States, is under the blow of a prohibition to give her blood for one six months period. The French Establishment of Blood also prohibits the blood donation throughout one one month after a voyage to the the United States.

History

According to American researchers, the epidemiologist John Marr and the microbiologist Charles Calisher , conquering it Alexandre Large the would have been victim, not Paludisme or Typhoid fever, but of the virus of the Western Nile. They base their assumption on a second reading of the account of the Greek author Plutarque and those of the other contemporary historians to the death of young the 32 year old emperor.

Until now, it was commonly allowed that its death had been caused, on its return of the Indian sub-continent, either by a poisoning, or by one of the many infectious illness which prevailed then in Mésopotamie. At the time to penetrate in Babylon, it tested the first signs of its mysterious disease, before succumbing two weeks, exhausted later by the conjunction of an increasing fever and a great weakening which will degenerate into Encéphalopathie.

In the lives of the famous men , Plutarque tells: “ When Alexandre was close to the walls of the city, it saw several corbels which fought with eagerness and it fell even some from there to its feet ”. According to the researchers, this observation which until now had passed unperceived, curiously recall the many deaths of birds observed in 1999, with the Zoo of Bronx or the Wildlife Conservation Park with New York, a few weeks before occurred of the first human cases of fever caused by the virus of the Western Nile.

The Mésopotamie, area of the current Iraq, regularly flooded by the risings of the Tiger and the Euphrate, is a harbor of choice for the Culex mosquito. However certain detractors object that the epidemics of fever are currently only observed in July whereas Alexandre Large the is deceased with ego of May. It is nevertheless to note that certain years the first cases appear as of June.

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