A second human case of the West Nile virus – also called Western Nile – has been detected in Lattes (Hérault). 14 horses have also been infected. In the Petite Camargue area, this virus originating from Uganda, brought by migratory birds and transmitted by mosquitoes, is actively circulating. Could it become endemic? Answer with researchers.
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This is a virus that is starting to develop south of Montpellier (Hérault). West Nile has affected a second person in Lattes, a few days after a first human case was detected in Baillargues. 14 horses have also been affected. This development of the virus raises questions.
For 15 years, EID scientists have been studying mosquito populations using CO2 traps, such as on the banks of the Méjean pond in Lattes. Now they share their catches, particularly to detect the West Nile.
In Montpellier, it is CIRAD researchers who collect these catches. Every year, tens of thousands of mosquitoes from 60 different species are analyzed.There are 1 in 1000 female mosquitoes that are infected with West Nile.” introduces Serafin Guttierez, virologist researcher at CIRAD in Montpellier.”There is one species that interests us because it is a vector. That is what I am looking for in all these individuals.“
The affected mosquitoes are then crushed to extract the virus.Then there are purification steps to recover the gene. This is what is analyzed using a PCR test.” continues the researcher. Like the Covid tests, the result is known after 1 hour 30.
“On this plate we see that there is a positive sample” says Patricia Gil, virology research engineer at CIRAD. This time, the Usutu virus was detected: very similar to the West Nile, it is also transmitted by mosquitoes.
Patricia Gil is responsible for analyzing the results of the PCR tests on these mosquitoes.
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© Bastien Moignoux / FTV
Despite these results and these increasing cases, it is still too early to certify that West Nile is endemic.We still have to check whether the strains are the same as in previous years.” nuances Patricia Gil.
However, “the same variant circulates regularly in the region” deduces Serafin Guttierez, for whom “he probably moved in with us“In Italy, dozens of cases are detected every year.
In 80% of cases, the virus is asymptomatic for humans. The remaining 20% may suffer from flu-like symptoms. And less than 1% of patients develop serious forms requiring hospitalization. “If the virus grows, the likelihood of people getting sick increases” recalls Serafin Guttierez, vigilant.
As with the proliferation of dengue fever in summer, surveillance methods could be put in place in the coming years.
(With Sébastien Banus)
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