-Analysis-

TOULOUSE — Right now the priority is to heal and repair the harm done by the swift and brutal emergence of COVID-19. But in time, we'll need to shift our attention from treatment to prevention, and that means having to redefine of our public health policies to make the resurgence of such pathologies less likely.

Preventive policies will have to draw lessons from the rise and management of recent pandemics, starting with the novel coronavirus but including the bird and swine flus that strike at regular intervals. These actions will have to be based on scientific facts, detached from short-term economic interests, and take stock of the roles meat consumption and intensive animal farming play in generating epidemics.

Zoonoses — or pathogens passing between fauna and humans — constitute 60% of all infectious diseases worldwide, and cause 2.5 billion cases of illness among people, annually. Three quarters of new pathogens detected in recent years were of animal origin.

This is not a new phenomenon: The Spanish flu of 1918, one of humanity's deadliest pandemics, originated in birds. Other well-known infectious diseases like smallpox, measles, whooping cough or mumps probably originated in domesticated animals.

The intensity of meat production in commercial circuits also make them into facilitators of pathogenic transmission.

The big epidemics that have struck since the late 20th century include many that emerged from livestock farming: Creutzfeldt-Jakob ("mad cow") disease, linked to beef (1986); the Nipah virus originally transmitted by bats but proliferating through pig farming (1998); multiple flu episodes of avian origin (H5N1, 1997 and 2004, and H7N9 in 2016); or the swine flu (H1N1, 2009).

Other epidemics may have originated in the consumption of wild animals, including COVID-19 (pangolins or bats), Ebola (bush meat or bats) and the AIDS virus (monkey meat).

Our elevated consumption of animal products also contributes to increased zoonosis indirectly. Meat-based nutrition needs more cultivation area than vegetarian nutrition, fueling deforestation and reducing the area available for wild species. Through hunting and transformation of wild habitats, humans and their livestock come into increased contact with wild animals and their attendant string of pathogens.

Faced today with heavy human losses and the colossal economic costs of such illnesses, we must question the evolution of our food production systems. Intensive animal farming effectively favors viral infections. Take boiler chicken for example, where overcrowding in premises typically involves 20 per square meter. Or the limited genetic diversity linked to globalized and standardized selectivity processes, which aids swift transmission inside and between farms. The intensity and global scale of fluxes of farmed animals and meat products in commercial circuits also make them into facilitators of pathogenic transmission.

Recurring zoonotic episodes show that future healthcare policies must inevitably combine human and animal health around a One Health principle. This would require considerable public resources to compensate farmers for economic losses, though judging by the recent multiplication of epidemics, even that would seem insufficient.

In fact, our societies are being dragged into an infernal spiral. As more and more animals are shut into smaller spaces, the danger of propagation is such now as to require preventive mass culls every time risks become imminent. In 2016, for example, South Korea culled some 10 million poultry to curb a bird flu episode.

As outside contact is the main threat in terms of contamination, farms confine animals with increasingly drastic containment measures. Wild animals are also eliminated to minimize contact and contamination risks, as happens with wild boars in Europe, for being potential bird flu vectors.

Use of veterinary medicines is separately a cause of collapse in wild animal populations. Diclofenac, for example — used to treat cows in India — may have decimated vultures by 95%, and that, in turn, prompted a rabies epidemic.

While it may be difficult, if not unrealistic, to prevent animal-to-human infections, control their appearance and manage their sanitary and economic consequences, one of the most efficient methods of reducing the risk of epidemics is to act "upstream," or reduce the number of animals that may be infected and to which we are exposed.

Preserving natural habitats, reducing meat consumption, cutting the size of intensive animal farms and ending (legal and illegal) sales of wild animal meat are thus, coherent and efficient measures for health care tomorrow or its One Health policies.

Reducing the risk of pandemics is just one of the very many benefits of adopting a vegetarian diet, cited in recent years in scientific reviews. These include reducing global warming gases and deforestation, reducing use of water, antibiotics and local farming pollution (like green algae), and reducing non-infectious diseases like cancer, diabetes and cardiovascular illnesses.

*Espinosa, Gaidet and Treich are researchers at the University of Rennes, the CIRAD in Toulouse, and the Toulouse School of Economics respectively.