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Lesson 3 min.
In recent months, cases of dengue fever have increased significantly in France. According to scientists, this development is yet another consequence of global warming. What should we expect?
This month of October is mild, perhaps a little too much. Beyond the relatively pleasant heat this autumn, you have no doubt noticed that mosquitoes are still present in many French regions. However, their presence is not anecdotal: according to the specialists of 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, a specialist in mosquito-related diseases interviewed by the newspaper 20 minutes, the situation is unprecedented:Tiger mosquitoes, vectors of diseases such as dengue, are still present, but at this time of year they should no longer be there“. And the consequences are quantified:
But if mosquitoes are so happy with us these days, it’s directly linked to global warming:
“Instead of having mosquitoes since 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 it stings again, it can re-inject this virus.
The phenomenon does not only concern France: it obviously extends beyond the borders. Thus, according to a Lancet countdown report (an annual study by 99 experts from 51 institutions), the window of opportunity for malaria transmission has increased by 32.1% in parts of the Americas and by 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 the invasion, the change initiated now appears inevitable: mosquito-related diseases, classically “exotic”, are now capable of being transmitted by a temperate mosquito in France. And the warmer it is outside, the shorter the mosquito development cycle will be.
“Between the egg and the adult it takes ten days. But if the temperature rises by for example 5 degrees, the cycle is reduced to eight days. In the future we will therefore have densities of mosquitoes that will increase since they will take 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 remain there permanently and will try to colonize other sites further north which will offer it a space where temperatures will be increasingly suitable.
What to do against mosquitoes?
In fact, there is a vaccine against dengue fever, produced by the Sanofi laboratory, but its effectiveness is currently considered too insufficient to recommend it to people who have never caught dengue fever. The strategy adopted today in France involves multiple “mosquito control” operations to destroy the centers of the larvae. Unfortunately, “tiger mosquitoes are resistant to the insecticides we use “, points out Anna-Bella Failloux.
At this stage, only vigilance seems to have an effect when traveling in regions where the heat persists: wear repellent, opaque clothing and avoid areas infested with mosquitoes.
