In general and according to the World Health Organization, health is defined as “A state of complete physical, mental and social well-being, which consists not merely in the absence of disease or infirmity”. From this perspective, health is seen as ‘human health’ and from the perspective of human diseases. And although this vision of health is indeed broad, it may seem incomplete in many respects.
What about the relationships between human health, animal health, and environmental health? What is the impact of biodiversity conservation on biology? Impact of climate change on health? Today, it is undeniable that human health is closely related to animal and plant health as well as environmental health.
The emergence of HIV, Ebola, Zika or even H1N1 influenza, as well as the consequences of air or water pollution, has shown that we cannot think of human health like an independent bubble that has nothing to do with the rest of the world. The COVID-19 pandemic, on its unprecedented scale, gives central place to the One Health approach, which invites us to erase the boundaries that still exist between human and veterinary medicine, plant biology and the environment.
Today, we have no scientific evidence that accurately explains the origin of the COVID-19 pandemic. But we do know that SARS-CoV-2, like 70% of emerging infectious diseases, is of animal origin. Virus sequencing data reveal that the closest known viral precursor to SARS-CoV-2 are coronaviruses circulating in groups of bats of the genus Rhinolophus (Horseshoe bats), a species that is endemic to parts of mainland China and Laos.
The bat has already been identified as the origin of SARS (due to SARS-CoV-1), but also of MERS (due to a very close coronavirus). However, bats have little contact with humans. We found an intermediate host, the civet in the SARS case and camels in the MERS case, and an as-yet-unrecognized host in the Covid-19 case.
In addition, if the epidemic is anthropogenic (that is, the result of extensive transmission of SARS-CoV-2 from one person to another in all groups of the planet), the fact remains that many species of mammals (cats, lions, tigers, ferrets, hamsters, deer, etc) some sensitivity to the virus, either after experimental exposure or in nature, after contact with an infected person.
At least 663 zoonoses (the name given to epidemics in animals) due to the human SARS-CoV-2 virus were reported in February 2022 to the World Organization for Animal Health (OIE, headquartered in Paris), with nine Ten of thirty species. Five countries around the world.
Animals infected by a man or a woman (this is called a reverse zoonosis) can also transmit the virus to other animals and in turn to other men or women. A famous case was that of a Danish mink farm in April 2020. The mustelids caught the virus from humans and transmitted it back to the farmers who tended them. More than 90% of minks were subsequently infected with the virus, and it is especially contagious in this species. 42% remained asymptomaticOthers suffer from mild forms of the disease.
All the unfortunate rodents (16 million individuals) were quenched in an emergency situation by the Danish authorities, who feared not only new human-to-human transmissions, but also the virus mutating to adapt to its host. The fear of creating an uncontrolled animal reservoir is due to the risks that could trigger a re-release of the epidemic and contribute to the emergence of new, particularly harmful variants.
The Anthropocene and the entropy
The Anthropocene, the new geological epoch in which we live today, is characterized by the advent of humans as a major force for change on Earth, overcoming geophysical forces. It is creating unprecedented planetary disruption, the consequences of which can be dire for our health.
Many examples. Deforestation has been extensive for several decades because it is essential to feed and house nearly 8 billion people on the planet. But this practice, to which poaching or even the search for gold is added, has contributed significantly to creating an unprecedented affinity with the world of wild animals, giving rise to animal diseases with the potential to lead to epidemics.
The same is true of intensive and unregulated animal husbandry in some countries, where exploited animals can act as viral reservoirs, if not hosts. These are able to double the infectious burden, even creating microbiological mutations in the origin of strains better adapted to humans, sometimes even 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 for agriculture.
In addition to zoonotic diseases, we have daily examples of weighing 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 It can be attributed to chronic exposure to fine particles that pollute the atmosphere). We are seeing more and more health consequences of climate change: an increase in infectious diseases (malaria, dengue, cholera, rift valley fever) and respiratory diseases, an increase in the mortality of people at risk from heat waves… Animals are of course also affected by climate change and air and soil pollution and water.
Another point of view
This vision may sound frightening, but it is no less realistic and should encourage us to act by thinking of health as a common common good, shared by the living. It’s not a question of relying on geoengineering — a term coined by Olivier Boucher, CNRS research director at the Dynamic Meteorological Laboratory, to designate “All techniques and practices implemented or planned with the aim of corrective large-scale effects of human stress on the environment”.
Indeed, this may be an approach likely to contribute to the vicious cycle of the Anthropocene. On the contrary, should we rather not change the paradigm and think more about prevention in the early stages and now consider health as a whole, for example by promoting the discourse about co-benefits?
Co-benefits are all interventions aimed at protecting the health of living organisms but also the planet. Thus, active commuting – walking, cycling and using public transportation – is excellent for our cardiovascular health, our carbon footprint, and the quality of the air we breathe.
The co-benefits are also reducing our consumption of red meat, which helps fight cancer risks and climate change. We know that livestock farming is responsible for the majority of greenhouse gas emissions from the agricultural sector, which produces a third of all carbon emissions on the planet.
In addition, livestock requires more deforestation using the water and energy we save by reducing our consumption. In our energy choices and in our home as well, a change in practices benefits respiratory health as much as the health of the planet. It’s time to change our habits. In addition to the participation 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 life sciences, human and veterinary medicine, and climate and environmental sciences talk together to redefine “A new way of inhabiting the world, learning to go around it to preserve it and thus ensure our survival”as Benjamin Coryat wrote in Pandemic, Anthropocene, and the Common Goodpublished in 2020.
Isn’t it time for an intergovernmental group of experts, like the Climate Alarm Group, to be dedicated to this new way of living in the world, sounding the alarm every time the Anthropocene continues to push the boundaries of respectful coexistence with the living? Preventing future epidemics will require robust public policy support with scientific knowledge and expertise in environmental and health issues.