The Provence-Alpes-Côte d’Azur Regional Health Agency announced on Monday, August 12, the identification of three cases of West Nile virus infection in the Var department.
This concerns a person in Ollioules, a person in Six-Fours-les-Plages and another in La Seyne-sur-Mer. An infected horse has also been identified.
What mode of transmission?
“West Nile virus infection is a viral disease, transmitted by mosquitoes (mainly of the genus Culex) which become contaminated exclusively through contact with infected birds (wild or domestic, editor’s note). Man and horse are ‘accidental hosts’’ of the virus. There is no transmission of the virus from human to human (or from horse to human) via the mosquito,” explains the ARS Provence-Alpes-Côte d’Azur in a press release published on August 12.
The tiger mosquito is not affected
The disease is mainly transmitted by the common mosquito in metropolitan France, the Culex mosquito. The female bites in the evening and at night, unlike the tiger mosquito which bites during the day.
In its press release, the ARS explains that it is seeking to identify the places where infected people are contaminated in order to identify possible sites of proliferation of the Culex mosquito.
Cases of transmission have also been described during organ transplants and blood transfusions.
What are the symptoms?
According to the Pasteur Institute, West Nile virus infection is asymptomatic in 80% of cases. In symptomatic cases, the disease is characterized by the sudden onset of a high fever occurring after 3 to 6 days of incubation.
“This fever is accompanied by headache and backache, muscle pain, cough, swollen glands in the neck, and often a rash, nausea, abdominal pain, diarrhea and respiratory symptoms,” adds the Institute.
Neurological complications occur in 1% of cases; meningitis and encephalitis. In even rarer cases, other complications such as hepatitis, pancreatitis or myocarditis may appear. “Usually, the patient recovers spontaneously, sometimes with after-effects. But the viral infection can be fatal, especially in older adults.”
Currently, there is no specific treatment for West Nile virus, management is symptomatic. There is a vaccine that protects the equine population but none for humans.
A virus first isolated in 1937
The West Nile virus is now considered to be the most widespread flavivirus – an RNA virus transmitted to humans or animals by arthropods, ticks or mosquitoes – after dengue fever, specifies the Pasteur Institute.
“It takes its name from the West Nile district of Uganda, where it was first isolated in 1937 from a woman suffering from a high fever. It was subsequently detected in humans, birds and mosquitoes in Egypt in the early 1950s, and has since been found in humans and animals in many countries.”
In France, the first human cases were detected in the early 1960s. Over the past fifteen years, the frequency of infections has accelerated. And the West Nile virus is now endemic in several European countries while its distribution area is expanding.*
Source : ARS Provence-Alpes-Côte d’Azur, Institut Pasteur
