Like every summer, mosquitoes have played the role of disrupting sunny days over the past few months. But more than in previous years, tiger mosquitoes transmitted dengue fever in France. From May 1 (start of the annual surveillance period) to September 20, 47 indigenous cases – therefore contracted in France – were identified by Public Health France (SPF). Three times more than in 2021 (14 cases) and without comparison with 2021 (only 2 cases).
“The situation is all the more exceptional as the figures are largely underestimated: most cases are asymptomatic and France has no culture of medical diagnosis of this type of viral disease”observes Yannick Simonin, lecturer in virology at the University of Montpellier.
According to the Ministry of Health, 75% of patients have no symptoms, the others may suffer from headaches, fever, body aches, even hemorrhagic shock for the most serious (1 to 5%). Treatments are essentially symptomatic (fight against fever, body aches), aspirin and non-steroidal anti-inflammatory drugs being contraindicated. Each diagnosed case must be reported to the Regional Health Agency (ARS).
Tiger mosquito implanted in 67 departments
If the number of imported infections is not changing much (193 in 2022 against 164 last year), the explosion of indigenous cases may be the result of two factors. First, the arrival on the national territory of patients due to the resumption of international exchanges after the confinement in the face of Covid-19. Their disease can then be transmitted in France, via new bites. But above all, the multiplication of the presence in France of tiger mosquitoes (or Aedes albopictus), which transmit dengue from human to human.
The insect with zebra-like bodies and legs took hold in 67 departments this year, compared to 51 in 2018. All of the indigenous cases were recorded in Provence-Alpes-Côte d’Azur (PACA) and Occitanie, 29 patients concentrating on a single focus in three neighboring municipalities, in the Alpes-Maritimes.
“Eventually, it will be on the whole of the metropolitan territory, all with a higher density in each region”, warns Yannick Simonin, specialist in arboviruses – viruses transmitted to humans by insects. An expansion that can be explained “less because of the rise in temperatures than of the climate observed this summer, with the alternation of dry periods – those of egg-laying – and heavy rainfall – favorable to mass hatching”.
Hundreds of arboviruses identified
Not to mention” emergency “the academic calls for « vigilance ». This would require identifying as closely as possible the cases of a source of contamination, in order to hope to carry out mosquito control in the area. A fight that will be always more complicated with the exponential multiplication of patients throughout the territory. Above all, behind dengue fever, the tiger mosquito raises the risk of spreading other arboviruses.
A hundred, transmitted by theAedes albopictus, has been identified. Some are subject to surveillance by health authorities, such as chikungunya (15 cases imported this year) and zika (2 cases imported). “But we could one day see the emergence of unknown viruses using the same vehicle, with en garde Yannick Simonin. Hence the importance of general surveillance of this territory’s tiger mosquito. »