In Montpellier, a first case of human infection with the Usutu virus was diagnosed. Transmitted by the bite of the Culex mosquito, the most predominant in France, the virus directly attacks the nervous system. What are the risks of contamination?
After dengue, zika and chikungunya, here is the Usutu virus. Transmitted by the bite of a Culex mosquito, this new virus which attacks the nervous system has just been discovered by researchers at Inserm in Montpellier. Viruses of African origin (Senegal, Nigeria, Uganda, Burkina Faso, Ivory Coast, Morocco …), Usutu mainly affectshe migratory bird species, such as blackbirds, chickadees, sparrows, robins and a few raptors, including the owl and owl. In Europe, the blackbird seems to be the main victim.
An essentially animal virus
The development cycle of the Usutu virus is still unknown to the scientific community, but it seems that these birds are the reservoir of the virus. Formally identified for the first time in South Africa in 1959, in Swaziland near the Usutu river (hence its name), it has been circulating in Occitanie since 2015.
It is believed to be the cause of several infectious outbreaks causing significant peaks in bird mortality, as in 2004 in Austria. Surprisingly, the number of sick or virus-positive birds often dropped spontaneously after an outbreak, suggesting that herd immunity is developing rapidly in surviving birds. However, no scientific study supports this hypothesis. Since 1996, several phenomena of mass bird mortality have been attributed to Usutu in the Italian provinces of Florence and Pistoia, as well as in Hungary, Switzerland, Spain or even Germany.
A first case of human infection in France
The first case of human infection in France was spotted in Montpellier. 39 year old man would indeed have been infected in France after a Culex-type mosquito bit migrating birds from Africa. “He arrived with a facial paralysis, explains to France 3 Olivier Sillam, the patient’s caregiver. His right side of the face could not move any more. He had ants all over his body, mainly on the right side and small motor deficits. A rather atypical picture for a classic facial paralysis “. Several human cases have been identified in Europe: 10 in Italy and three in Croatia. Positive point: the virus is not transmitted from man to man. There is therefore no risk of contamination.
How to recognize the Culex mosquito?
The Culex mosquito is the most predominant insect in France. Also nicknamed “domestic mosquito”, it can transmit serious diseases such as West Nile Fever or Japanese Encephalitis, as well as the Usutu virus, unlike the Anopheles mosquito, vector of malaria or the Aedes mosquito (which includes the tiger mosquito) which is a vector of dengue, Chikungunya and Zika. The Culex mosquito does not look like the tiger mosquito: it measures between 5 and 7 mm long and its wings protrude slightly from the abdomen, which is brown and ringed. The female’s body can become deformed when she is gorged with blood. It is besides that which stings the Man.
Like the tiger mosquito, the Culex appreciates rather warm and stagnant water and / or shady intraforest ponds or ditches and it is capable of biting in the middle of the day (unlike the Anopheles which only bites at night). It is therefore necessary to protect yourself in theory 24 hours a day, hence the interest of eliminating the breeding sites of your habitat, that is to say the slightest source of stagnant water, such as the bottom of gutters or even flowerpot saucers. It is indeed in these small quiet corners that the females lay their eggs.
Our times are in the midst of transition, particularly because of travel and global warming. It is therefore not surprising to see the emergence of a number of new diseases in France (“emerging diseases”) which previously only concerned distant countries.
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