Commonly and according to the WHO, health is defined as “a state of complete physical, mental and social well-being, which does not consist merely of the absence of disease or infirmity”. From this perspective, health is seen as “human health” and through the prism of diseases affecting human beings. This vision of health, although already broad, can then, in many respects, seem incomplete.
What about the interfaces between the health of human beings, that of animals and that of the environment? Of the impact of the preservation of biodiversity on the living? The impact of climate change on health? Today, it is undeniable that human health is intrinsically linked to animal and plant health as well as to environmental health.
The emergence of HIV, Ebola, Zika or even the H1N1 flu, as well as the consequences of air or water pollution, have already shown us that we cannot think of human health like an independent bubble with no connection to the rest of the world. The Covid-19 pandemic, by its unprecedented scale, gives a central place to the “One Health” approach, which invites us to erase the boundaries that still exist between human medicine, veterinary medicine, plant biology and ecology.
Today, we do not have scientific evidence explaining precisely the origin of the Covid-19 pandemic. But we know that SARS-CoV-2, like 70% of emerging infectious diseases, has an animal origin. Genetic sequencing data from the virus reveal that the closest known viral precursors of SARS-CoV-2 are coronaviruses circulating in populations of bats of the genus Rhinolophus (horse horseshoe bats), species endemic to parts of mainland China and Laos. .
The bat had already been identified as the origin of SARS (due to SARS-CoV-1), but also of MERS (due to another very close coronavirus). However, bats have little contact with humans. We have found an intermediate host, the civet in the case of SARS and the dromedary in the case of MERS, a host that has not yet been identified in the case of Covid-19.
In addition, if the pandemic is human (that is to say, it is the result of intense human-to-human transmission of SARS-CoV-2 in all populations of the planet), the fact remains that many species of mammals (cats, lions, tigers, ferrets, hamsters, deer, etc.) have shown some sensitivity to the virus, either after experimental exposure or in nature, after contact with an infected human.
No less than 663 epizootics (name given to epidemics in animals) due to human SARS-CoV-2 had been reported in February 2022 to the World Organization for Animal Health (the OIE, whose headquarters is in Paris), with nineteen species from thirty-five countries around the world.
Animals infected by the man or the woman (this is called reverse zoonoses) can also transmit the virus to other animals and in return to other men or women. A famous case was that of Danish mink farms in April 2020. The mustelids had contracted the virus from humans and transmitted it back to the farmers who cared for them. More than 90% of the mink had then been infected with the virus, which is particularly contagious in this species. 42% had remained asymptomaticthe others with mild forms of the disease.
All the unfortunate rodents (16 million individuals) were put down in an emergency by the Danish authorities, who feared not only new transmissions in humans, but also that the virus mutates to adapt to its host. The fear of the constitution of an uncontrolled animal reservoir is due to the risks that it will relaunch the pandemic and contribute to the emergence of new particularly virulent variants.
Anthropocene and entropy
The Anthropocene, or the new geological epoch in which we are today, is characterized by the advent of humans as the main force of change on Earth, overriding geophysical forces. It creates an unprecedented planetary disorder, the consequences of which on our health can be dramatic.
Many are the examples. Deforestation has been massive for several decades because it is necessary to feed and house nearly 8 billion people on the planet. But this practice, to which are added intensive poaching or even gold panning, has notably contributed to creating an unprecedented proximity with the wild animal world, which results in the emergence of zoonoses likely to give rise to pandemics.
The same goes for intensive and unregulated animal husbandry in some countries, where the animals exploited can act as viral reservoirs, if not as amplifying hosts. These are capable of multiplying the infectious load, even of creating microbiological mutations at the origin of strains better adapted to human beings, sometimes more virulent. They can also develop bacterial resistance to the antibiotics with which they are treated on farms – half of the antibiotics produced on Earth are intended for farming.
Beyond zoonoses, we have daily examples of the weight of the consequences of human activity on our health – and on the health of living organisms in general.
We know the effects of air pollution, from asthma attacks to cancers (6 to 11% of lung cancer deaths would be attributable to chronic exposure to fine particles polluting the atmosphere). We are seeing more and more health consequences of climate change: increase in infectious diseases (malaria, dengue fever, cholera, Rift Valley fever) and respiratory diseases, increased mortality of vulnerable people caused by heat waves… Animals are of course also affected by climate change and air, soil and water pollution.
Another point of view
This vision may seem frightening, but it is no less real and should encourage us to act by thinking of health as a universal common good, shared by the living. It is not a question of relying on geo-engineering – a term coined by Olivier Boucher, CNRS research director at the dynamic meteorology laboratory, to designate “all the techniques and practices implemented or planned with a large-scale corrective aim of the effects of anthropogenic pressure on the environment”.
Indeed, this would be an approach likely to contribute to the vicious circle of the Anthropocene. On the contrary, shouldn’t we rather change the paradigm, think more about prevention upstream and now consider health as a whole, for example by promoting the discourse on co-benefits?
The co-benefits are all the interventions that aim to protect the health of living organisms but also that of the planet. Thus, active mobility – walking, cycling, using public transport – is excellent both for our cardiovascular health and for our carbon footprint and the quality of the air we breathe.
The co-benefits are also the reduction of our consumption of red meat, which helps to fight against the risk of cancer and against climate change. We know that livestock farming accounts for the majority of greenhouse gas emissions from the agricultural sector, which produces a third of all carbon emissions on the planet.
In addition, the livestock requires more deforestation by using water and energy that we would save by limiting our consumption. In the area of our energy choices and our habitat too, the change in practices benefits our respiratory health as much as that of the planet. It is time to change our habits. In addition to the involvement of governments and international organizations, the co-benefits place the citizen at the heart of the action against climate change.
It is therefore urgent in this context that life sciences, human and veterinary medicine, climate science and ecology speak and work together to redefine “a new way of inhabiting the world, of learning to curl up in it to preserve it and thereby ensure our own survival”as Benjamin Coriat writes in The pandemic, the anthropocene and the common goodpublished in 2020.
Isn’t it time to set up an intergovernmental group of experts, like the one that sounds the alarm on the climate, and which would be devoted to this new way of living in the world, sounding the alarm each time that the Anthropocene will continue to exceed the limits of a respectful cohabitation with the living? Preventing future pandemics will require strongly backing public policies with the knowledge and expertise of science in environmental and health matters.