Dengue fever alert in France, in the wake of the tiger mosquito

The acrid smell falls slowly, but it takes in the throat. Fortunately, at this hour, it does not bother many people. It is 5:45 am, Tuesday September 20, and the pick-up of the Interdepartmental Agreement for Mosquito Control (EID) begins its slow circuit in the streets of La Gaude (Alpes-Maritimes). Flashing lights, the roar of the compressor: the procession shakes up the tranquility of a deserted late night in this village in the hinterland of Nice. The hunt for tiger mosquitoes is on. First, the main roads, then the secondary roads. The nebulized liquid spurts out in thick waves and draws swirls in the light of the streetlamps. The wind, light this morning, moves them towards the hedges, the gardens and the green spaces which line the tracks. Deltamethrin droplets settle on any surface they encounter. It is this pesticide from the pyrethroid family that clears the throat.

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

“It’s an insecticide, not tap water…”, acknowledges Grégory L’Ambert, EID manager of the preventive fight against Aedes albopictus, the scientific name of the tiger mosquito. “But by treating between 4 a.m. and 8 a.m., with a product that degrades rapidly under the effect of heat and the sun, we avoid bothering the population too much, but also affecting other species, and in particular pollinators », assures this 40-year-old medical entomologist. Usually based in Montpellier, he has been sailing in this sector of the Alpes-Maritimes since the beginning of September. At the heart of a triangle of a few square kilometres, formed by the bordering municipalities of Saint-Jeannet, Gattières and La Gaude, is currently developing the largest outbreak of autochthonous dengue fever ever seen in metropolitan France. Thirty-one cases officially recorded by the Provence-Alpes-Côte d’Azur (PACA) regional health agency (ARS) as of September 21. Nearly a dozen in the process of being confirmed. “It is unprecedented… In the end, we risk reaching fifty cases”, worries Grégory L’Ambert, watching the sun rise over La Gaude.

Unpublished. In a press release published on Wednesday September 21, the table drawn up by the French public health agency (SPF) does not say anything else. The 31 cases officially listed in the focus of the Alpes-Maritimes explode the counters well. So far, the maximum had been reached in Nîmes, in 2015, with eight people infected. Broadening the focus leads to the same observation: across France, forty-seven cases of autochthonous dengue fever have already been recorded this summer, spread over five outbreaks, where the peak peaked at fourteen cases in 2020. “Beyond the number of cases, this year 2022 is characterized by the extension of the risk on the metropolitan territory with the occurrence of outbreaks in departments hitherto spared: Pyrénées-Orientales, Hautes-Pyrénées and Haute- Garonneinsists SPF. Previously, the cases had mainly occurred in the Var, the Alpes-Maritimes, the Hérault, the Gard. »

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