AIDS, Ebola, Mpox, Chikungunya, Zika, Covid-19… The number of infectious diseases linked to zoonoses, that is to say pathologies transmitted by animals to humans, have been growing steadily for around forty years. . Many studies show that the risk increases as humans destroy natural habitats, in particular because it amplifies contact between humans and wild animals. Several scientists are warning about the subject, like Serge Morand, health ecologist and researcher at the CNRS, who is worried about the health repercussions of the TotalEnergies oil megaproject in Uganda and Tanzania.
Deforestation paves the way for potentially pathogenic microorganisms for humans
“As part of the major EOACOP project (East African Crude Oil Pipeline Project), TotalEnergies wants to extract oil from more than 400 wells drilled in Uganda, including 132 in a nature reserve, and create an oil pipeline more than 1,400 km long, impacting thus all biodiversity and local communities”, describes Serge Morand.
The scientist points out that this project will, among other things, lead to the construction of many roads, high CO2 emissions (up to 34 million tons per year estimated) and the destruction of forests. However, the consequences of this human pressure on the environment are not limited to the loss – already tragic – of many plant and animal species.
“It is a threat to human health because there is a risk of new infectious diseases emerging! And for good reason, the forest allows balance, it contributes to many things: the regulation of the climate, the well-being of local communities, the maintenance of biodiversity… but also the regulation of the transmission of infectious agents which circulate in the within wildlife. At the international level, it has been observed that one of the first factors linked to the emergence of all kinds of diseases was deforestation. We can cite malaria, leishmaniasis, viral diseases such as Ebola or the Marburg virus disease in Africa.”
Problem, it is difficult for the scientific community to predict what could happen. “It’s a real research challenge! We know there is going to be something but we don’t know what, where and when… and bad surprises are very likely. In the case of Mpox, for example, it was not at all predictable. We saw its emergence in the 70s in West Africa, but it was finally last year that it made headlines. Luckily this virus is not smallpox, it is not very virulent… But what is worrying is that it succeeded in no time in adapting to humans and moving all over the planet thanks to the ways of globalization. So we can try to protect ourselves at the borders, as for Covid-19, but what should be done instead is prevention directly at the sources, by protecting the tropical forests.”
Pandemic: when do we spot the emergence of a viral disease?
“Viruses that have a high mortality rate are quickly spotted, but those that are moderately virulent can circulate under the fire of the radars before we realize that there is a strong international transmission, as with the coronavirus. It is all the more complicated to regulate in these countries where there is already a lack of dispensaries and doctors to treat the local population. Prevention must therefore also go in this direction, by strengthening their healthcare systems.”
While some viruses take time to emerge because they need several mutations and/or recombinations to adapt to humans, others are on the contrary able to do so very quickly. “It depends on the evolution. Some viruses only need a few modifications to have greater infectivity or virulence capabilities. And when we look at the number of viruses that we know, we have actually characterized few of them… So potentially, there are still many that have the capacity to infect humans and cause human-to-human transmission.”