Tropical viruses in Occitania: why are Usutu and West Nile becoming “endemic” in our region?

Without being alarmist, a study shows that it is advisable to be vigilant in the face of these tropical viruses which establish themselves durably in Occitania.

Occitania is becoming a land conducive to the establishment of two viruses: the West Nile which had raged in the region in 2015 but which we have known since the 1960s and a less known virus, the Usutu which is, he too, of African origin and who arrived on regional soil through migratory birds. First in the Camargue but we now find them comfortably established in the Montpellier region in urban and peri-urban areas.

Low-noise traffic

Usutu is currently responsible for around a hundred cases of infection in humans in Europe and was identified in France for the first time in 2018 in Montpellier in a patient hospitalized at the CHU for facial paralysis.

And even if it remains rare for it to spread to humans and is mainly responsible for high bird mortality, “it must be carefully monitored. There is no outbreak to fear, no need to be alarmist but there is a quiet circulation both in birds, but also in humans and animals like dogs or horses. It’s probably becoming ‘endemic’ in our area.”notes the scientist Yannick Simonin, lecturer at the University of Montpellier.

He led a comprehensive study with around 20 researchers for ECDC’s European Journal of Infectious Disease Surveillance, Epidemiology, Prevention and Control.

Heavy traffic in 2018

The conclusions are unambiguous: these viruses take root in the south of France and this is probably one of the effects of global warming “which promotes the emergence of viruses that were intended to remain in tropical areas”notes the specialist.

During the summer of 2018, in Europe but especially in France near the Mediterranean, a strong circulation of the West Nile and Usutu viruses was identified: “We have had nearly 2,000 cases from West Nile in Europe, including nearly 400 deaths (mainly related to neurological damage) and probably also cases in Occitania, but this circulation has gone largely unnoticed in our region”remembers Yannick Simonin.

Limit proliferation

Like dengue fever, chikungunya or Zika, transmitted by the tiger mosquito, these viruses are transmitted by the common mosquito. Otherwise called the culex pipiens, its life cycle passes through tropical birds and then local birds such as blackbirds or passerines. Faced with these diseases, there is no vaccine or treatment. The only way to protect yourself: avoid the proliferation of mosquitoes by depriving them of water.

The One Health study, conducted by these scientists, provides a better understanding of how these viruses can reach humans through precise monitoring and mapping of their proliferation.

If a case is detected, it is possible to treat the outbreak with appropriate treatments directed against mosquitoes to limit its spread. “The scientific community is proactive: we monitor, we control”concludes Yannick Simonin.

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