Nature sustains us. It’s where we originated. The lesson from this pandemic is not to be afraid of nature, but rather to restore it and understand how to live with it.
COVID-19 it’s not the first pandemic of my lifetime. Many of adults had lived through the influenza pandemic in 1918. And in recent years we have all followed the news nervously as Ebola, SARS, and MERS have surfaced in human populations in Africa, Asia, and the Middle East.
Except for polio, which is transmitted only from human to human, most of those disease agents were part of natural cycles that involved only animals. They spilled over into humans because nature was disturbed in some way. There is a lesson in that.
We shouldn’t be surprised by the continuing emergence of new diseases—some with pandemic potential—if humanity continues with its wholesale destruction of nature.
A classic example, but perhaps less familiar these days, is yellow fever. It was once a scourge in many American countries, including Brazil. The problem is not only yellow fever: Deforestation in the Amazon also creates breeding sites for the hosts and vectors of afflictions like malaria and schistosomiasis. And the problem isn’t confined to Brazil or any other single place. As the COVID-19 pandemic has devastatingly shown, modern transportation systems can quickly whisk some human pathogens around the world—and also plant and animal pests and diseases. As I write, a Chinese coal ship in Baltimore harbor was discovered (in the nick of time) to have egg masses of the Asian gypsy moth, which is a known pest for at least 500 plant species.
To epidemiologists and virologists the COVID-19 pandemic is no real surprise. A very close relative of the SARS virus, the novel coronavirus also thrives in bats, which are largely immune to its ill effects. A wildlife market in Wuhan, China, is where the spillover from animals to humans probably happened, and the initial jump from a wild bat to an animal that was acquired and consumed by a human may well have happened there too. Such markets are a nightmare of animal mistreatment, with appallingly crowded and unsanitary conditions— just an ideal festering potpourri for generating new viral threats.
The possibly origin of the virus
Based on their genomic sequencing analysis, Kristian Andersen, PhD, an associate professor of immunology and microbiology at Scripps Research and his collaborators concluded that the most likely origins for SARS-CoV-2 followed one of two possible scenarios.
In one scenario, the virus evolved to its current pathogenic state through natural selection in a non-human host and then jumped to humans. This is how previous coronavirus outbreaks have emerged, with humans contracting the virus after direct exposure to civets (SARS) and camels (MERS). The researchers proposed bats as the most likely reservoir for SARS-CoV-2 as it is very similar to a bat coronavirus. There are no documented cases of direct bat-human transmission, however, suggesting that an intermediate host was likely involved between bats and humans.
In this scenario, both of the distinctive features of SARS-CoV-2’s spike protein — the RBD portion that binds to cells and the cleavage site that opens the virus up — would have evolved to their current state prior to entering humans. In this case, the current epidemic would probably have emerged rapidly as soon as humans were infected, as the virus would have already evolved the features that make it pathogenic and able to spread between people.
In the other proposed scenario, a non-pathogenic version of the virus jumped from an animal host into humans and then evolved to its current pathogenic state within the human population. For instance, some coronaviruses from pangolins, armadillo-like mammals found in Asia and Africa, have an RBD structure very similar to that of SARS-CoV-2. A coronavirus from a pangolin could possibly have been transmitted to a human, either directly or through an intermediary host such as civets or ferrets.
Then the other distinct spike protein characteristic of SARS-CoV-2, the cleavage site, could have evolved within a human host, possibly via limited undetected circulation in the human population prior to the beginning of the epidemic. The researchers found that the SARS-CoV-2 cleavage site, appears similar to the cleavage sites of strains of bird flu that has been shown to transmit easily between people. SARS-CoV-2 could have evolved such a virulent cleavage site in human cells and soon kicked off the current epidemic, as the coronavirus would possibly have become far more capable of spreading between people.
Another expert Andrew Rambaut cautioned that it is difficult if not impossible to know at this point which of the scenarios is most likely. If the SARS-CoV-2 entered humans in its current pathogenic form from an animal source, it raises the probability of future outbreaks, as the illness-causing strain of the virus could still be circulating in the animal population and might once again jump into humans. The chances are lower of a non-pathogenic coronavirus entering the human population and then evolving properties similar to SARS-CoV-2.
Some people are viewing the pandemic as nature fighting back against all that has been and continues to be done to it. But it is human behavior and disrespect for nature that have been the cause. Furthermore, as we cope with the pandemic, climate change is marching ahead. It’s causing strong ripples of change in all ecosystems and probably tipping the balance in favor of pathogens currently unknown to us.
The wise way forward is to invest in conservation and science, and to embrace nature and the glorious variety of life with which we share this planet. A healthy future for humanity and a healthy biodiverse planet go hand in hand.
