The current pandemic is the sixth major one to hit humanity since the Spanish flu of 1918. But the frequency and severity of these global epidemics may well accelerate in the coming years due to our lifestyles and the incredible adaptability of viruses. Several experts are sounding the alarm.
“Future pandemics will be more frequent, spread faster, cause more damage to the global economy, and kill more people than Covid-19 if nothing is done. That’s the warning cry of the IPBES (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) in its latest report, issued in December 2020.
There is no great mystery about the cause of the Covid-19 pandemic or other modern pandemics,” says Peter Daszak, chair of the EcoHealth Alliance and chair of the IPBES workshop. Changes in land use, agricultural expansion and intensification, and unsustainable trade, production, and consumption are disrupting nature and increasing contact between wildlife, livestock, pathogens, and humans. This is a pathway that leads directly to pandemics.
827,000 viruses have the ability to infect humans.
Most of the new viral pandemics are caused by zoonotic diseases which are caused by pathogens that jump species from animals to humans. For instance, Tuberculosis [caused by the bacterium Mycobacterium tuberculosis] originated in cattle and was transmitted to humans when cattle were first kept in the Neolithic period. There are an estimated 1.7 million undetected viruses currently found in mammals and birds, 827,000 of which may have the ability to infect humans, according to IPBES.
Fortunately, not all of them will succeed. To cause a pandemic, the virus must cross two species boundaries: It must acquire the ability to infect a human cell and then replicate effectively. This is not easy, because the cellular machinery in humans and animals is very different. This is currently the case with avian viruses: they are responsible for thousands of deaths, can infect humans, but have not yet crossed the second threshold above which transmission to humans is possible. But, it’s only a matter of time. For instance, HIV which came from a chimpanzee took hundreds of years to cross the barrier. The virus made dozens of attempts before it could mutate enough, to start the global AIDS pandemic.
A typical pandemic virus at a glance
In 2013, Jean-Claude Manuguerra, head of the biological emergency unit at the Pasteur Institute, described what the next emerging pathogen that could trigger the next great epidemic of the 21st century would look like: an RNA virus “endowed with great genetic plasticity and contagious by respiratory transmission, of zoonotic origin, and that would have reached humans several times with a single success in a region where major changes in land use have occurred. First, it would have been propagated in humans without the knowledge of the health authorities”. A portrait that bears a striking resemblance to SARS-Cov-2 in the emergence of Covid-19.
The great pandemics of the past (Leprosy, plague, cholera…) were mostly associated with bacteria. Thanks to improved hygiene and antibiotics, these types of pandemics have almost disappeared. However, we are much more threatened by viruses, whose genetic plasticity is a crucial factor in the transition from one species to another.
SARS-Cov-2 reached humans after likely lying dormant for years in a reservoir animal – it is now known that the virus likely originated in a bat, where it shed from other lineages 40 to 70 years ago.
livestock farming poses a Huge threat
But why should the threat be greater today? As IPBES reminds us, greater proximity to animals significantly increases the risk of a pandemic. Intensive animal farming, in particular, is a real-time bomb. Thousands of genetically homogeneous animals, crammed together in one place, are the ideal conditions for the virus to evolve and make the mutations necessary to adapt to humans.
We can also see the extent to which zoonotic diseases can cause damage to livestock. In 2019, swine fever decimated a quarter of the world’s pig population, killing animals in a matter of days. All it would take is for the virus to cross the species line, and that would be a disaster. It’s not such a crazy scenario: in October 2020, researchers discovered that SADS-CoV (Swine acute diarrhea syndrome coronavirus) is capable of infecting and replicating in human cells.
Anticipating risk, mission impossible?
In his report, IPBES also mentions ecosystem disruption or global warming, but the link between cause and effect is less clear. In any case, the scientists call for radical changes in epidemic prevention. “Responding to diseases only after they occur with public health measures and technological solutions is a slow and uncertain path, fraught with human suffering and costing tens of billions of dollars each year,” they write.
The experts call for, among other things, the establishment of a council to anticipate high-risk areas and identify research gaps, or a reduction in consumption patterns, globalized agricultural expansion, and trade, for example through taxes or levies on meat consumption, livestock, and other high-risk pandemic activities.
Will this be enough to prevent a future global pandemic? I am not sure. Given the number of viruses that are potentially pathogenic to humans, it is very unlikely that we are able to create a prevention plan for each of them. As for the end of industrial agriculture, that’s not scheduled for tomorrow. Unfortunately, viruses will always be one step ahead.