How environmental crises put France under the threat of new diseases

Enough to make hypochondriacs nightmare. The National Agency for Food, Environmental and Occupational Health Safety (ANSES) alerted on June 1 to the possible emergence in France of Crimean-Congo hemorrhagic fever (CHF). Already present in Spain, this virus risks arriving in France with global warming linked to human activities, and in particular the consumption of fossil fuels.

Mainland France is increasingly exposed to new diseases due to environmental crises. However, it would be simplistic to explain their emergence solely by global warming, warns franceinfo Jean-François Guégan, director of research at the Research Institute for Development and the National Research Institute for Agronomy, l food and the environment. The specialist points to globalization, deforestation, livestock farming or even land use, which often have more important roles. “Translation comes mainly through economic exchanges”he decides.

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The threat that CHF Canada represents is well borne by global warming. This disease is transmitted by the Hyalomma tick, which appreciates dry climates and hot periods, which explains its usual presence in Asia and Africa. This tick, carried in particular by migratory birds, has already been found on the soil of France for decades, explains to franceinfo Elsa Quillery, coordinator of scientific expertise at ANSES. However, it had not managed to settle there due to weather conditions that were unfavorable to its survival. But climate changes, especially in the south of France, are now changing the situation. “She likes the garrigue, the maquisexplains the specialist. We know that it goes up along the Rhone Valley. We find it in the south of Drôme and Ardèche.”

Crimean-Congo hemorrhagic fever in same category as Ebola

Since 2013, in Spain, twelve people have contracted CCHF. No specific treatment exists for this disease, which is characterized first by flu-like symptoms, body aches, digestive disorders, vomiting and then possibly haemorrhages. Among these twelve patients, four died. A high mortality rate, notes Elsa Quillery.

In France, this disease of “significant gravity” And “highly contagious” must be declared, reports to franceinfo Harold Noël, epidemiologist at the infectious diseases department of Public Health France. Suspicions of CCHF, a disease classified in the same category as Ebola virus disease, fit “in a dedicated signaling and processing circuit”with some “referring infectiologists in reference health establishments”underlines the expert. “Usually, a sample is sent to a specialized laboratory and the results reach us within eight hours.”

For the moment, the CCHF virus has not been detected in Hyalomma ticks collected in France, underlines Elsa Quillery noting that the human can only be a “accidental host” of the tick. By 2050, with global warming, the area of ​​implantation of this tick could considerably extend in France, increasing the risk of bites and the possibility of infection.

The tiger mosquito, vector of tropical diseases

For the tiger mosquito and the diseases it can transmit (namely dengue fever, chikungunya and the Zika virus), the role of global warming is more nuanced. These diseases that are usually found in tropical regions are now found in France. Sixty-five cases of dengue fever were identified in France in 2022. “These sporadic cases do not trigger epidemics”comments to franceinfo Hélène Soubelet, director of the Foundation for Research on Biodiversity.

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But contrary to popular belief, it is not thanks to global warming that the tiger mosquito has arrived in our latitudes, settling in almost all of France. It was in fact transported by man or by goods, underlines Jean-François Guégan. The tiger mosquito has thus won the various French regions by taking the road, via trucks and cars. “He lives within a radius of 200 to 300 meters. It would take him a phenomenal time to do Marseille-Lyon. But with the motorway, it only takes 2h30”smiles the specialist in the relationship between environment and health.

If global warming is not to blame for the arrival of the tiger mosquito in France, it will nevertheless play a role in the maintenance of dengue fever, chikungunya, and Zika. The transmission of these diseases is indeed not optimal when the temperature is below 26°C. In a context in which hotter summers nibble away at spring and encroach on autumn, we risk witnessing a stretching of the period of the year during which these viruses can flourish.

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The distribution in France of diseases transmitted by the tiger mosquito remains nevertheless difficult to predict. “It is difficult to project into the future, especially for the south of France”, remarks to franceinfo the American ecologist Camille Parmesan. This member of the Intergovernmental Panel on Climate Change (IPCC) reports that, for now, studies on the subject contradict each other. Some conclude that they will spread, others estimate that the aridity anticipated in the decades to come will probably prevent the vectors of these diseases (mosquitoes, gnats, ticks, lice) from remaining there.

On the other hand, the one who is also research director at the CNRS explains that these diseases are more likely to circulate more in the north of France, as well as in other regions where the drying out should be more moderate than in the south of France. ‘Europe. “Climate change is driving a general northward shift in the range of diseases and their vectors”she develops.

The “tangible” threat of an avian virus affecting humans

Jean-François Guégan, however, judges that focusing on global warming and the idea of“a movement of tropical diseases from the south to the north is unfortunate”. “Everything that happens to us today comes more from the east, from China or even Vietnam”says the research director, which particularly targets avian flu.

Since epidemics affecting animals have hit the country heavily in recent years, respiratory diseases related to poultry (influenza birds) are closely monitored in France. In the Southwest, 900,000 animals were slaughtered in May. “The level of circulation of avian influenza observed in France over the past two years is unprecedented. It is really very important”confirms Harold Noel.

The main fear of experts is that these viruses cross the species barrier, via other animals such as pigs, and end up affecting humans. This phenomenon, called zoonosis, is favored by the proximity between humans, livestock and wild animals, and would be less pronounced if human activities did not exert such strong pressure on ecosystems.

In this table, a family of viruses worries more than others. “Influenza viruses are uniquely equipped to be emerging viruses. Their ability to adapt their genome to infect hosts is unparalleled”, raises Harold Noël. Hélène Soubelet shares this concern: “In all plans for the prevention of serious outbreaks, there is the hypothesis that an avian virus hybridizes with a human influenza virus”explains the director of the Foundation for Research on Biodiversity.

“The problem is that the avian virus is very deadly and the human virus is very transmissible. If you have the combination of the two, it multiplies the problems that we had during the Covid-19 pandemic. “

Hélène Soubelet, Director of the Foundation for Research on Biodiversity

at franceinfo

“We are prepared for it. Besides, we had not planned for Covid-19 but human avian flu”notes Hélène Soubet. “It’s something that will happen. The probability is almost 100%. We just have a hard time knowing when”she says.

The threat is “ tangible”abounds Harold Noël. “This is why a program is being put in place to be able to limit the bird risk as much as possible, and detect possible transmissions as quickly as possible to people who are closest to the animals, that is to say breeders in general, he explains. If such a focus did not appear in France, it is not at all excluded that this virus could cross borders. All the ingredients for a new pandemic.