Responsible for making recommendations on the government’s health policy, Covars looked at diseases likely to represent a high risk in France by 2030. And the spectrum is wide…
What are the new threats weighing on us in the short term, and how can we prepare for them? This is the meaning of the opinion published on April 9 by the Committee for Monitoring and Anticipation of Health Risks (Covars), entitled “Assessment of the risks of major exceptional situations for human health in France during the years 2025-2030” .
Vigilance is focused “mainly” on “zoonoses”, which pass from animals to humans, and “arboviruses”, transmitted in particular by mosquitoes. With one certainty: beyond the already observed impacts of heat peaks and the increase in “extreme” events (floods, drought, storms, etc.), climate change will change the situation, as the ecologist explains. Patrick Giraudoux, professor emeritus at the University of Franche-Comté and member of Covars.
You say that global warming will cause a multiplication of disease vectors. For what ?
For a simple reason: the periods of favorable conditions for certain vectors will lengthen. Take the example of mosquitoes. Until now, in winter, they are at rest, and the length of the summer season only allows them to have a few reproduction cycles. If it gets hot earlier and later, these cycles mechanically multiply. You do “x2, then “x2”, then “x2” again, and you have an exponential that sets up…
Ultimately, we risk having much larger mosquito populations, therefore many more bites and increased chances of disease transmission.
What worries us the most at the moment is dengue. While it was previously a tropical disease, we are now seeing indigenous cases in the southwest and southeast of France – a phenomenon also facilitated by increased travel.
Patrick Giraudoux (ecologist, member of Covars)
There is also chikungunya, transmitted by the tiger mosquito. It is possible that the metropolis will be faced with a major epidemic, similar to the one that has already hit Reunion Island. The same goes for the Zika virus, which has circulated widely in South America.
For the same reason, ticks, which are among other vectors of Lyme borreliosis, will also multiply in significant proportions.
Photo Nicolas Barraud
Should we also fear the arrival of new species, not yet established on our soil?
Indeed, with these new conditions, certain species will be able to move further north, until they colonize our territory. This is the case, for example, of the “Hyalomma” tick, which carries a virus that is quite serious for human health, which causes Crimean-Congo fever. Its impact has already been confirmed in Spain. It has now arrived north of the Pyrenees and will, in all likelihood, move up into the Rhône valley and spread across the entire country. We therefore have both a new species and a new disease.
We must add to this the fact that certain species, regardless of global warming, manage to adapt to conditions that were not initially favorable to them. This is the case of the tiger mosquito, which was able to gradually invade Europe.
On another front, the quality of the air we breathe is expected to continue to deteriorate, as is the quality of the water…
Concerning the air, vigilance is focused, among other things, on ozone, the concentration of which increases with sunshine – hence the peaks that we very often observe in summer, in large cities. This is problematic because it is an oxidant that potentiates respiratory infections.
As for water, as it becomes rarer, it will also become more concentrated. Consequence: the concentration of chemical pollutants and pathogenic organisms will inevitably increase, to the point of making certain deposits undrinkable.
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With what consequences?
If you have one bacteria per cubic meter, the risk of being contaminated – for example by Escherichia coli – is low. If you have thousands, the risk becomes high. On the other hand, in certain very degraded conditions, populations will be pushed to fetch water where it is not drinkable, for lack of an alternative. We could then witness epidemics of cholera, particularly overseas.
Can the collapse of biodiversity also be a factor of uncertainty, or even increased risks for our health?
This is an essential point, which is often underestimated and misunderstood. In an ecosystem you have thousands or even hundreds of thousands of species. If you remove just one, it won’t be obvious. However, this disappearance will leave an empty ecological niche. The species that were previously in competition with it will therefore expand their perimeter and take the place left vacant. These are called opportunistic species.
Let’s take the simplified example of a system with seven species. You take away three. Let’s imagine that one of the remaining species takes advantage of this to expand its reach and increase its biomass in terms of population. The consequence is an impoverishment of biodiversity: the same species, relatively homogeneous on a genetic level, will take over the others.
It is then enough for any microbe to emerge for us to have a “magnificent” incubator of viruses, bacteria, etc. The mechanism is the same whether it is plants or animals.
Patrick Giraudoux (ecologist, member of Covars)
Photo Renaud Baldassin
In the case of agrosystems, the same species is often cultivated, very monoclonal and therefore not very diversified, for obvious reasons of productivity. A species of this type will be very vulnerable to parasites, fungi and other insect pests. To counter this fragility, conventional agriculture uses phytosanitary products, with all the public health problems that this poses.
Impoverished biodiversity is therefore much more difficult to manage than a very diverse environment. The whole becomes extremely variable and sensitive to any external disturbance, whether changes in temperature, drought or disease.
Is Man’s growing influence on nature likely to make things worse?
It’s a certainty. If we consider the biomass, or weight of all mammals on a planetary scale, we humans represent 36%, and our domestic animals, 60%. 96% of this biomass is therefore composed of approximately twenty species. The remaining 4% are wild mammals, which include no less than 6,500 species!
The very structure of this system is conducive to pandemics: from wild animals, we easily pass to domestic animals, which play the role of incubators, and then to humans, whose biomass is absolutely considerable.
Faced with these multiple warning signals, is our alert and prevention system sufficient?
This is the whole challenge posed by the opinion given by Covars, which recommends being much more proactive than what is being done today. We will have to think about improving what already exists, in the face of situations which are ultimately quite predictable.
Some things work well, but given the number and scale of the changes to come, we will have to prepare much more in advance, to avoid reacting when there is a fire at home.
Patrick Giraudoux (ecologist, member of Covars)
From this point of view, Covid was a sort of dress rehearsal. It is a pathogenic virus, of course, but the mortality rate is not that high – about ten times more than seasonal flus, which, without being negligible of course, remains much lower. than for certain tropical viruses.
We must therefore take the threat very seriously and prepare for it. The question is not whether there will be pandemics in France in the near future – there will be, that’s certain – but to be ready when they arrive.
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Comments collected by Stéphane Barnoin
