What is this deadly disease that has come to France?

The Provence-Alpes-Côte d’Azur regional health agency announced on Monday, August 12, that three cases of West Nile virus infection had been detected in the Var department.

This involved one person in Orlyoules, one in Six-Fort-les-Plages and another in La Seyne-sur-Mer. A contaminated horse was also found..

What is the mode of transmission?

“West Nile virus infection is a viral disease transmitted by mosquitoes (mainly Culex spp.) which are contaminated only by contact with infected birds (wild or domestic, ed.). Humans and horses are accidental hosts‘ Viruses are not transmitted from person to person (or from horse to person) by mosquitoes.” ARS Provence-Alpes-Côte d’Azur explained in a press release issued on August 12.

Tiger mosquitoes don’t care

The disease is mainly spread by the Culex mosquito, which is common in mainland France. The female mosquito bites in the evening and at night, unlike the tiger mosquito, which bites during the day.

ARS explained in its press release that it is seeking to identify the site of contamination by infected individuals in order to determine possible sites of spread of Culex mosquitoes.

Cases of transmission have also been described during organ transplantation and blood transfusion.

What are the symptoms?

According to the Pasteur Institute, 80% of West Nile virus infections are asymptomatic. In symptomatic cases, the disease is characterized by a sudden onset of high fever after a 3-6 day incubation period.

“This fever is accompanied by headache and back pain, muscle pain, cough, swollen lymph nodes in the neck, and often rash, nausea, abdominal pain, diarrhea and respiratory symptoms,” The institute added.

Neurological complications occur in 1% of cases; meningitis and encephalitis. In more rare cases, other complications may occur, such as hepatitis, pancreatitis and even myocarditis. “In general, patients recover on their own, sometimes with sequelae. But viral infections can be fatal, mainly in the elderly. »

There is currently no specific treatment for West Nile virus, only symptomatic treatment. There is a vaccine that protects horses, but there is no vaccine that protects humans.

Virus first isolated in 1937

The Pasteur Institute notes that West Nile virus is currently considered the most widespread flavivirus (an RNA virus transmitted to humans or animals by arthropods, ticks or mosquitoes) after dengue fever.

“It is named after the West Nile region of Uganda and was first isolated in 1937 from a woman with a high fever. It was found in humans, birds and mosquitoes in Egypt in the early 1950s and has been found in humans and animals in many countries since then.”

The first human cases were discovered in France in the early 1960s, and infections have increased in frequency over the past 15 years. Although the distribution of West Nile virus is expanding, it is currently endemic in several European countries.*

source: ARS Provence-Alpes-Côte d’Azur, Institut Pasteur