In France, diseases transmitted by mosquito bites seem too remote a risk to worry about. However, on 31 October, Santé Publique France already counted 65 cases of native dengue fever for the year 2022. Today, dengue has also reached Corsica, with the first case detected on 4 October 2022.
Worldwide, the World Health Organisation counts 50 million cases of dengue per year, and half the world’s population is now at risk of contracting dengue. Cases of severe dengue fever, also known as dengue haemorrhagic fever, are mainly identified in Latin America and Asia.
In this article, we answer the main questions: What is dengue fever? What are its symptoms? How does it arrive and spread in France? And above all, how can we limit the risks?
Dengue fever usually occurs in tropical areas such as Martinique, Guadeloupe, French Guiana and the islands of the Indian and Pacific Oceans. The climate there is particularly favorable to the proliferation of disease-carrying mosquitoes. The heat and humidity are ideal conditions for tiger mosquitoes to breed and lay their eggs.
We regularly have cases of dengue fever in mainland France, involving people returning from trips to tropical areas. These are known as imported cases.
Today, dengue fever also affects people who have not left French territory in the weeks preceding the onset of symptoms: indigenous cases. The tiger mosquito is a disease vector: it can transmit the virus from an imported case to a person who has not travelled.
The native cases detected mainly concern the south of France:
Dengue fever is a non-contagious virus. The diseas is mainly transmitted by mosquito bites. More exceptionally, however, it can be transmitted from person to person by transfusion or organ or cell transplantation.
Dengue fever is transmitted by the Aedes albopictus mosquito vector, also known as the tiger mosquito. It is also transmitted by the Aedes aegypti mosquito, although the latter is not present in Europe. The female mosquito can produce up to five egg-laying cycles. For each of these cycles, she needs to replenish her blood supply. If she is interrupted during a blood meal, she will bite again until she obtains enough blood for her eggs. If a female mosquito bites several people, including a person carrying the dengue virus, she will transmit it. This is how we go from imported cases of dengue fever to indigenous cases.
In 50-90% of cases, dengue fever is completely asymptomatic. In the opposite case, the first symptoms of dengue fever appear on average 4 to 7 days after the bite of the mosquito carrying the virus.
And more rarely:
Despite these disabling symptoms, dengue fever is not dangerous. However, this virus does present a risk of haemorrhage. This is why non-steroidal inflammatory treatments and aspirin are contraindicated.
Today, the dengue vaccine has been granted marketing authorisation in Europe, but is not available in France. Dengue fever is relatively rare in mainland France. In mainland France, the strategy adopted to combat dengue fever is vector control, via mosquito control.
By eliminating tiger mosquitoes, we are limiting the risk of dengue being transmitted throughout France. In towns where dengue is detected, the ARS carries out two successive mosquito control operations, one week apart. This corrective treatment is carried out after cases of native dengue have appeared.
Qista offers a preventive treatment, reducing the population of tiger mosquitoes before they can transmit dengue fever. The idea is to install anti-mosquito trap close to areas where mosquitoes are proliferating. The mosquitoes are attracted by a lure, specific to each species, then sucked up by the machine and captured in the net. As the trap is connected, it can be used to transmit data on mosquito catches, so that changes in mosquito populations can be mapped. With this data, local authorities can improve the targeting of field operations and carry them out at the right time.
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