Dengue alert in France, following the tiger mosquito

The pungent smell falls slowly, but it clings to the throat. Fortunately, at this hour, she doesn’t bother many people. It is 5:45 am on Tuesday, September 20, and the collection of the Interdepartmental Agreement for the Control of Mosquitoes (EID) begins its slow circuit through the streets of La Gaude (Alpes-Maritimes). Flashing lights, the roar of the compressor: the procession shakes the tranquility of a deserted night in this town in the hinterland of Nice. The hunt for tiger mosquitoes is underway. First the main roads, then the secondary roads. The nebulized liquid sprouts in thick waves and draws eddies in the light of the street lamps. The wind, light this morning, moves them towards the hedges, the gardens and the green spaces that border the slopes. Deltamethrin droplets settle on any surface they find. It is this pesticide from the pyrethroid family that clears the throat.

Between 5 and 8 in the morning, an EID car equipped with a cold fog generator crosses the streets of La Gaude (Alpes-Maritimes), on September 20, 2022.
Marc Raselli and Ali Abdelkadous, EID operators, use a thermal fogger in a private house, in La Gaude (Alpes-Maritimes), on September 20, 2022.

“It’s an insecticide, not tap water…”, recognizes Grégory L’Ambert, responsible for the EID of the preventive fight against aedes albopictus, the scientific name of the tiger mosquito. “But by treating between 4 and 8 in the morning, with a product that degrades rapidly due to the effect of heat and sun, we avoid bothering the population too much, but also affecting other species, and in particular pollinators”, assures this 40-year-old entomologist. Regularly based in Montpellier, it sails in this sector of the Maritime Alps from the beginning of September. In the heart of a triangle of a few square kilometers, formed by the bordering municipalities of Saint-Jeannet, Gattières and La Gaude, the largest outbreak of autochthonous dengue ever seen in metropolitan France is currently taking place. Thirty-one cases officially registered by the regional health agency (ARS) of Provence-Alpes-Côte d’Azur (PACA) as of September 21. Almost a dozen in the process of confirmation. “It is unprecedented… In the end, we run the risk of reaching fifty cases”, Grégory L’Ambert worries, watching the sun rise over La Gaude.

Unpublished. In a press release published on Wednesday, September 21, the table prepared by the French public health agency (SPF) says nothing more. The 31 cases officially listed in the Alpes-Maritimes outbreak well exploit the counters. Until now, the maximum had been reached in Nimes, in 2015, with eight people infected. Broadening the focus leads to the same observation: throughout France, forty-seven cases of autochthonous dengue have already been recorded this summer, spread over five outbreaks, where the peak reached fourteen cases in 2020. “Beyond the number of cases, this year 2022 is characterized by the extension of the risk in the metropolitan territory with the appearance of outbreaks in hitherto unscathed departments: Pyrénées-Orientales, Hautes-Pyrénées and Haute-Garonne.insist SPF. Previously, the cases had occurred mainly in the Var, the Maritime Alps, the Hérault, the Gard. »

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