Like the tick, the sandfly (small gnats present in the south-east of France) and nearly 400 of the 3,500 species of mosquitoes existing in the world, the tiger mosquito is a vector of disease. To do this, he must first become infected, taking the pathogen by sucking some blood from a sick person.
“The female mosquito will then be able to transmit it to a healthy subject during a new blood meal. It takes several days for a mosquito to become infective, that is to say that the virus crosses the digestive barrier, multiplies and pass in his saliva”specifies the National Agency for Food, Environmental and Occupational Health Safety (Anses).
What diseases can the tiger mosquito transmit?
“The tiger mosquito can be a vector of many viruses such as dengue, Zika or chikungunya”, specifies ANSES.
Initially contained in tropical or subtropical zones, dengue is the viral disease most commonly transmitted by Aedes albopictus on French soil.
According to the Pasteur Institutethis virus manifests itself suddenly following 2 to 7 days of incubation by the appearance of a high fever often accompanied by headaches, nausea, vomiting, joint and muscle pain and a rash resembling that measles.
Rather rare, its complications can nevertheless be severe and lead to lethal bleeding.
If the symptoms of Zika are mostly benign (rash, moderate fever, fatigue, etc.), “the virus can cause birth defects if infected during pregnancy”warns Public Health France.
As for chikungunya, native to Africa, Asia and the Indian subcontinent, its symptoms resemble a flu-like state: fever and severe joint pain.
Indigenous cases, imported cases
“These viruses are introduced into France by travellers: businessmen, tourists…”notes Didier Fontenille, member of the Committee for monitoring and anticipating health risks (Covars) and medical entomologist specializing in these vector-borne diseases.
When these people arrive in metropolitan France and develop symptoms there following being contaminated by a mosquito abroad, we then speak of imported cases.
In France, from May 1 to December 9, 2022, Public Health France identified 272 imported cases of dengue fever (imported from 41 countries, Cuba and India in the lead), 22 of chikungunya (mainly contracted in Indonesia and Brazil) and 2 of the Zika virus.
In Paca, Public Health France thus identifies 35 imported cases of dengue fever and 1 case of chikungunya.
More worrying, the Provence Alpes-Côte d’Azur region has the highest number of indigenous cases recorded in France in 2022.
From May 1 to December 9, 52 people contracted dengue there without having previously traveled to a contaminated area, out of 65 nationally.
A ripple effect of the influx of tourists, potentially virus carriers, and tiger mosquitoes to transmit these imported cases to local residents.
In the Alpes-Maritimes, at the end of August, an outbreak of 34 cases was thus declared around Saint-Jeannet, another of 10 cases in Saint-Laurent-du-Var and Cagnes-sur-Mer. .
In the Var, 7 cases were also declared in the same home, in Fayence, at the end of June.
“With the El Niño phenomenon, all the lights are red”, Didier Fontenille, member of Covars
“We expect an increase in cases in the years to come, in the South of France and in particular around Nice, which is clearly a hotspot city for the tiger mosquito. The Committee for monitoring and anticipating health risks ( Covars) recently publicly warned regarding it”recalls Didier Fontenille.
An increase in contamination due to an addition of factors: “After the Covid-19 epidemic, international travel resumed on a massive scale. Global warming also comes into the equation by reducing the incubation time of viruses in the tiger mosquito and accelerating the hatching of larvae. However, more there are tiger mosquitoes, the greater the risk of contamination.”
Scientists are also worried regarding the impact of a climatic phenomenon at work on the side of the tropical Pacific Ocean. Called El Niño, this warming of the surface of ocean waters can cause prolonged droughts, floods and increases in tropical storms and cause a butterfly effect to our coasts.
“It will affect the West Indies, Reunion Island, South America. We are currently monitoring it like milk on the fire. Because it will lead to an increase in epidemics elsewhere in the world… which should necessarily be ‘import into mainland France by travellers, particularly via Nice, a major tourist hub. All the lights are red”warns Didier Fontenille.
“Finally, human behavior, which we do not see changing significantly, is another aggravating factor”warns the medical entomologist, who recalls that Aedes albopictus proliferates above all thanks to the stagnant water of our balconies and gardens (saucers under flower pots, watering cans, uncovered water collectors, etc.).
Simulation exercises and Orsec Plan
Faced with this increased risk of an increase in cases, the Health Risk Monitoring and Anticipation Committee is preparing to “multiply large-scale intervention simulations”, explains Didier Fontenille.
Especially since a strong concern of outbreaks of sources of contamination is looming with the approach of the 2024 Olympic Games, which will transform Paris into a Tower of Babel. “Or the Rugby World Cup this year [dont des matchs auront lieu à Nice]“warns the entomologist.
“The Covars must verify that we have the technical and human capacities to intervene in outbreaks of contamination on a larger scale. Until then, we intervene around each case. But if we go from 65 indigenous cases to 500 or even 1,000 , this strategy will no longer be able to work. The idea is to work on a Orsec map“concludes Didier Fontenille.
