Covid-19, a natural agent for regulating human activity?

While the controversy over the origin of Covid-19, natural or human and accidental, is in full swing, the scientific community is resolutely leaning towards a natural source of the virus.

Covid-19 would thus be a "zoonosis," that is to say, an infectious disease, of bacterial, viral, or parasitic origin, transmissible from animal to man. Therefore, the problem has an ecological dimension; its examination will allow us to put all the pieces of the puzzle together for a holistic vision of the case: from cause to effect.

At the World Health Organization (WHO), many UN institutions and international NGOs have consistently pointed out that the Covid-19 pandemic is only a symptom of biodiversity mistreated by human activity. But how? When did it start?

Reservoirs and intermediate hosts

From the Neolithic era (between 10,000 and 5,000 years before our time), humanity experienced enormous demographic, economic, and cultural upheavals. This period corresponds to the adoption of a sedentary lifestyle and the gradual shift from a subsistence mode based on hunting and gathering to agriculture and livestock. The domestication of animals involved frequent contact between humans and animals, as well as with their bodies. These contacts provided many opportunities for ancient populations to contract diseases. "Neolithization" is considered in the history of our species, which is barely 300,000 years old, as a high point in human expansion long before industrialization and globalization. During the entire pre-antibiotic period, when health precautions were not required, diseases emerging from promiscuity between humans and animals put the human immune system to the test and selected (it is indeed the selection Darwinian) the individuals most resistant to these diseases.

If there are currently more than 150 zoonoses, these are not new to humans. Advances in hygiene and health have made it possible during the twentieth century to reduce and even eradicate many infectious diseases. However, despite this progress, new diseases are still appearing, or old diseases are re-emerging. By citing these diseases, we will realize that the intervals of eruptions are closer and more and more deadly: rabies, Ebola, AIDS, H1N1, avian flu, SARS, MERS-CoV, Zika, etc.

Before going on to humans, these viruses most often infect one or more animal species, which constitute the natural reservoir of this virus. The bat, for example, is considered to be a natural reservoir for many of these diseases. When an emerging disease appears, it is because a pathogenic agent has, on the one hand, come into contact with the new host, sometimes asymptomatic carrier, and on the other side that it has succeeded in crossing what is called the species barrier (through the phenomenon designated by the English term "spillover"). Often its genome undergoes modifications that make it capable of multiplying and propagating within this new species. In the case of the coronavirus responsible for MERS-CoV, which raged in 2012 in the Arabian Peninsula, the dromedary acted as an intermediate host before this virus was transmitted to humans. In the case of the severe acute respiratory syndrome (SARS) in 2003, it was a civet, while the pangolin is for the moment among the leading "suspects" concerning Covid-19.

Anthropocene

In their reservoir species, a precise balance is established between the viruses and its host, where, as a survival strategy, the viruses are kept in slow motion until an opportunity arises to find a new host. However, man, with his social lifestyle, his dense and ultra-connected cities, offers in this respect the best of opportunities to conquer the planet! And that's what happened with the Covid-19.

Each living species has its procession of viruses. Their impact on the reproduction, growth, or survival of their hosts potentially makes them important regulatory agents in communities and ecosystems. Each species occupies a specific ecological niche, and each time one proliferates without restraint and becomes dangerous for the balance of the ecosystem, the "parasitic police" is activated. Viruses, for example, therefore seize the opportunity to be easily transmitted when the host individuals are very numerous and overcome more than 90% of these hosts. This system of monitoring and self-regulation is a recurring natural process of millions of years old. Would he be regulating the human population today with the Covid-19? Will we be a species like any other in this ecological system obeying the laws of evolutionary biology?

The world population estimated at nearly 2.6 billion in 1950 reached the level of 7 billion in 2011 and will reach 9.7 billion in 2050! Since the industrial revolution of 1850, man has acquired such an influence on the biosphere that he has become its central actor, going so far as to change the face of our planet through its exaggerated activity. This is the notion of Anthropocene, etymologically meaning "the age of Man." The latter continues to spill over into the territories of wildlife, which he unscrupulously excludes. With the disruption of the functioning of ecosystems, cleared forests, returned and mined soils, poached species ... we are increasing the risks of zoonoses and their evolution into epidemics or pandemics.

A few months of confinement were enough for our planet to breathe, for the animals to bring down their fear and return to claim their former territories. A few months of confinement were sufficient for many of us to relearn how to listen to birds, to observe from our windows the hatching of flower buds and the stealthy movement of animals ...

Let us make sure that this lesson serves us well say there is a before and after the Covid-19. Let's think about our responsibility. Let's reconsider our consumption, our travels, our leisure. Let's reduce our ecological footprint, be united with each other, and with the species we meet.

For the French version, please view it here on L’Orient Le Jour.