Commonly and according to the WHO, health is defined as “a state of complete physical, mental and social well-being, not consisting merely of the absence of disease or infirmity”. In this perspective, health is seen as “human health” and under the prism of diseases that affect human beings. This view of health, although already broad, can therefore, in many respects, seem incomplete.
What about the interfaces between the health of humans, animals and the environment? The impact of preserving biodiversity on the living? The impact of climate change on health? It is now undeniable that human health is inextricably linked to animal and plant health as well as 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 as an independent bubble with no connection to the rest of the world. The Covid-19 pandemic, due to its unprecedented scale, gives a central place to the “One Health” approach, which invites us to erase the borders that still exist between human medicine, veterinary medicine, plant biology and ecology.
Today, we do not have scientific evidence that precisely explains the origin of the Covid-19 pandemic. But we know that SARS-CoV-2, like 70% of emerging infectious diseases, is of animal origin. Genetic sequencing data from the virus reveal that the closest known viral precursors of SARS-CoV-2 are the coronaviruses circulating in populations of bats of the genus Rhinolophus (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 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.
Furthermore, if the pandemic is human (that is, it is the result of intense human-to-human transmission of SARS-CoV-2 in all populations on the planet), the fact is 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 the wild after contact with an infected human.
No less than 663 epizootics (name given to epidemics in animals) by human SARS-CoV-2 were notified in February 2022 to the World Organization for Animal Health (OIE, based in Paris), with nineteen species from thirty-five countries around the world. around the world.
Animals infected by the male or female (this is called reverse zoonoses) can also transmit the virus to other animals and in turn to other males or females. A famous case was that of Danish mink farms in April 2020. Mustelids contracted the virus from humans and passed it on to the farmers who took care of them. More than 90% of mink have been infected with the virus, which is particularly contagious in this species. 42% remained asymptomaticthe others with mild forms of the disease.
All the hapless rodents (16 million individuals) were culled in an emergency by the Danish authorities, who feared not only new transmissions to humans, but also that the virus would mutate to adapt to the host. The fear of the constitution of an uncontrolled animal reservoir is due to the risks of relaunching the pandemic and contributing to the emergence of new, particularly virulent variants.
Anthropocene and entropy
The Anthropocene, the new geological epoch in which we find ourselves today, is characterized by the advent of man as the main force for change on Earth, overcoming geophysical forces. It creates an unprecedented planetary disorder whose consequences for our health can be dramatic.
There are many examples. Deforestation has been massive for several decades because it is necessary to feed and shelter about 8 billion people on the planet. But this practice, in addition to intensive poaching or even gold mining, has notably contributed to creating an unprecedented proximity to the wild animal world, resulting in the emergence of zoonoses that can lead to pandemics.
The same goes for intensive and unregulated livestock farming in some countries, where exploited animals can act as viral reservoirs, if not amplifying hosts. These are capable of multiplying the infectious load, even creating microbiological mutations in the origin of strains more adapted to humans, sometimes more virulent. They can also develop bacterial resistance to the antibiotics they are treated with on farms – half of the antibiotics produced on Earth are destined for agriculture.
In addition to 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 that pollute the atmosphere). We are seeing more and more health consequences of climate change: increase in infectious diseases (malaria, dengue, cholera, Rift Valley fever) and respiratory diseases, increased mortality of vulnerable people caused by heat waves… Animals are also naturally 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 thinking of health as a universal common good, shared by the living. It is not about relying on geoengineering – a term coined by Olivier Boucher, CNRS research director in the dynamic meteorology laboratory, to designate “all techniques and practices implemented or planned with the objective of correcting on a large scale the effects of human pressure on the environment”.
Indeed, this would be an approach that would likely 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 of co-benefits?
Co-benefits are all interventions that aim to protect the health of living organisms, but also that of the planet. So active mobility – walking, cycling, using public transport – is great for both our cardiovascular health and our carbon footprint and the quality of the air we breathe.
The co-benefits are also reduced consumption of red meat, which helps fight cancer risk and climate change. We know that livestock is responsible for most greenhouse gas emissions from the agricultural sector, which produces a third of all carbon emissions on the planet.
In addition, ranching requires more deforestation using water and energy that we would save by limiting our consumption. In the area of our energy choices and also our habitat, changing practices benefits both our respiratory health and that of the planet. It’s time to change our habits. In addition to the involvement of governments and international organizations, co-benefits put the citizen at the center of action against climate change.
It is therefore urgent in this context that the 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 thus guarantee our own survival”as Benjamin Coriat writes in The pandemic, the Anthropocene and the common goodpublished in 2020.
This is not the time to create an intergovernmental group of experts, like the one that sounds the alarm about the climate, and that would dedicate itself to this new way of living in the world, sounding the alarm every time the Anthropocene continues to exceed the limits of respectful coexistence. with the living? Preventing future pandemics will require strong public policy support with the knowledge and experience of science in environmental and health issues.