"The Covid-19 pandemic is closely linked to the issue of the environment."

The decline in biodiversity accelerating the emergence of viruses that are dangerous for human populations increases the risks of pathogen transmission and the emergence of associated diseases, sixteen leaders of scientific organizations said in a forum at "Le Monde".

The current Covid-19 pandemic cruelly reminds us of the fact, too long neglected in both research priorities and public policy, that human health, animal health and ecosystem health are closely linked, that one does not go without the others, as underlined by the interdisciplinary "One Health" approach.

Coronaviruses belong to the huge family of coronaviridae, which are naturally circulating among many animal species, with effects ranging from harmless to deadly. They are viruses with RNA [ribonucleic acid], which means that they are very prone to mutations, and with a very long genome, which means that they are prone to recombination.

Four types of benign coronaviruses are already known in humans to affect the respiratory system (reportedly responsible for 15-30% of common colds) and, more rarely, the gastrointestinal, cardiac and nervous systems.

Three other types cause serious infections: SARS-CoV, known to have caused an outbreak of acute pneumonia in humans in 2002-2003, SARS-CoV2, which is close to the previous one and responsible for the current pandemic, and MERS-CoV, which occurred in the Middle East in 2012.

Recombination between two different viruses

Genetic analyses show that SARS-CoV-2 belongs to the same group of Betacoronaviruses as RaTG13, isolated from a bat from the Chinese province of Yunnan. More recently, an even closer virus has been isolated from Malaysian pangolin. The particular region of the virus protein that allows it to infect human cells has 99% identity with SARS-Cov-2 (compared to only 77% for RaTG13, which is not able to directly infect humans). This suggests that SARS-Cov-2 is the result of recombination between two different viruses, one close to RaTG13 and one closer to pangolin.

A first lesson from this finding on the probable origins of the virus is that there would be no point in eradicating pangolins or bats. Viruses of this family run through the entire mammalian biodiversity, which includes many healthy carriers.

Since animals are largely involved in the emergence of new epidemics, one might be tempted to think that biodiversity represents a potential danger since it harbours many pathogens. In reality, the opposite is true, as a high diversity of potential or actual host species limits virus transmission through a dilution effect. Moreover, the genetic diversity specific to each species contributes to the emergence of host resistance to its pathogen, and thus also limits its transmission.

It is indeed the decline in biodiversity which, by reducing host populations and thus the likelihood of the emergence of resistance, increases the risks of pathogen transmission and the emergence of associated diseases.

Numerous examples

A second lesson is that targeting human activities that directly impoverish biodiversity is a public health necessity. The pangolin is one of the most poached and threatened species, which is particularly the case for the Malaysian pangolin, classified as Critically Endangered.

Its trade is strictly prohibited, yet more than 20 tonnes are seized worldwide each year, which suggests the scale of the total traffic. The consumption of meat and the incorporation of its scales into traditional Asian medicine are the main reasons for this massacre, and the exponential increase in contact with humans. Bats, pangolins and humans have little reason to be promiscuous in the wild.

It is hunting and gathering them in a market place that is the only explanation for the transition from bats to pangolins and then from pangolins to humans. The Covid-19 pandemic is closely linked to the issue of the environment: it is indeed, once again, a human disturbance of the environment and of the human-nature interface, often amplified by the globalisation of trade and lifestyles, which accelerates the emergence of viruses that are dangerous for human populations, through recombination between viruses of different species.

There are many examples, such as the hunting and poaching of wild (or even protected) species, which breaks the food security barrier (Ebola, SARS, Covid-19) or habitat destruction, which brings humans into close proximity with endemic pathogens, such as Buruli ulcer in French Guiana, where the disease strikes humans in a way that is believed to be harmful to the environment, and the human-nature interface, often amplified by the globalisation of trade and lifestyles, which accelerates the emergence of viruses that are dangerous for human populations through recombination between viruses of different species.
Neglected Evolutionary Biology

The export of contaminated bushmeat to regions with high human density (Ebola), the intensification of passenger and freight transport across the globe against the backdrop of global warming are promoting the widespread geographical spread of pathogens or pathogen vectors (dengue, zika, chikungunya) as well as changes in their spatial distribution (malaria).

More than ever, the One Health concept must become a priority for interdisciplinary research, breaking down the still all-too-familiar barriers between the biomedical and environmental science worlds.

In the light of the health crisis we are going through, it is paradoxical to note that studies in medicine and pharmacy continue to largely ignore the biology of evolution, and that it has recently become optional for two thirds of a high school student's schooling.

Managing the current crisis, as well as better anticipating those that are bound to occur in the near future, implies consolidating the foundations of a health ecology that addresses the interdependencies between the functioning of ecosystems, socio-cultural practices and the health of human, animal and plant populations taken together. Finally, it implies drawing practical and political consequences from the knowledge it brings us without waiting for the next crisis.

Signatories : Elsa Cortijo, Director of Basic Research at the French Atomic Energy and Alternative Energies Commission (CEA); Bruno David, President of the National Museum of Natural History; Michel Eddi, Chairman and CEO of the Centre for International Cooperation in Agricultural Research for Development (CIRAD) ; Mehdi Ghoreychi, Scientific Director of the Institut national de l'environnement industriel et des risques (Ineris); François Houllier, Chairman and CEO of the Institut français de recherche pour l'exploitation de la mer (Ifremer); Hélène Jacquot-Guimbal, President of the Gustave-Eiffel University; Nathalie Lemaitre, Scientific Director of the Institute for Radiological Protection and Nuclear Safety (IRSN); Philippe Mauguin, Chairman and CEO of the French National Institute for Agriculture, Food and the Environment (INRAE); Jean-Paul Moatti, President of the AllEnvi alliance; Jean-Marc Ogier, President of the University of La Rochelle; Michèle Rousseau, President of the Bureau de recherches géologiques et minières (BRGM); Virginie Schwartz, President and CEO of Météo France; Stéphanie Thiébault, Director of the Institut écologie & environnement (INEE-CNRS); Valérie Verdier, President and CEO of the Institut de recherche pour le développement (IRD).

The signatories are all members of the board or council of AllEnvi, the National Environmental Research Alliance.