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Dengue fever cases have increased sharply in France in recent months. According to scientists, this development is yet another consequence of global warming. What should we expect?
This month of October is mild, probably a little too much. Beyond the relatively pleasant heat of this autumn, you have no doubt noticed that mosquitoes are still present in many French regions. However, their presence is not anecdotal: according to specialists from the Pasteur Institute, it would be reasonable to expect an increase in viruses classified as “exotic” on our soil.
Too many mosquitoes
For Professor Anna-Bella Failloux, specialist in mosquito-related diseases interviewed by the daily 20 minutes, the situation is unprecedented:Tiger mosquitoes, vectors of diseases such as dengue fever, are still present, but they should no longer be there at this time of year”. And the consequences are quantified:
But if mosquitoes are so happy with us these days, it is directly linked to global warming:
“Instead of having mosquitoes from the beginning of May, we will see them from April. And they will stay later after the summer is over”predicts the specialist.
These undesirables actively participate in the spread of dengue, chikungunya… By biting a human, the tiger mosquito absorbs blood, letting the virus pass inside its body into its salivary glands. When he stings again, he can re-inject this virus.
The phenomenon does not only affect France: it extends of course beyond the borders. Thus, according to a Lancet Countdown report (an annual study conducted by 99 experts from 51 institutions), the window of opportunity for malaria transmission has increased by 32.1% in parts of the Americas and 14% in Africa over the past decade. Globally, the risk of dengue fever transmission has increased by 12%!
What can we expect in the future?
Should we therefore fear the next seasons and/or expect to suffer from unknown viruses in the decade to come? Not to mention invasion, the change initiated now appears inevitable: diseases linked to mosquitoes, classically “exotic”, are now capable of being transmitted by a temperate mosquito in France. And the hotter it is outside, the shorter the mosquito’s development cycle will be.
“Between the egg and the adult, it takes ten days. But if the temperature increases for example by 5 degrees, the cycle is shortened to eight days. In the future, we will therefore have mosquito densities that will increase since it will take them less time to become adults” explains the specialist in 20 minutes.
Climate change will also offer them more space to colonize. Today, the tiger mosquito is installed in the south of France. It will stay there permanently and try to colonize other sites further north which will offer it a space where the temperatures will be more and more suitable.
What to do against mosquitoes?
There is indeed a vaccine against dengue fever, produced by the Sanofi laboratory, but its effectiveness is considered too insufficient to date to recommend it to people who have never caught dengue fever. The strategy adopted today in France involves more “mosquito control” operations to destroy the centers of larvae. Unfortunately, “tiger mosquitoes are resistant to the insecticides we use”, emphasizes Anna-Bella Failloux.
At this stage, only vigilance seems to produce effects when traveling in regions where the heat persists: wear a repellent, covering clothes and avoid areas infested with mosquitoes.