So how did it start, this "Chinese virus" our president keeps referring to?
I hope this brief scientific review can put this pandemic into a proper perspective.
Viruses are infectious agents that cannot survive or multiply on their own. So they hijack the DNA or RNA, protein-making mechanisms of other living organisms to thrive. But they first have to attach to and then pry open the host cell membrane. This mutual affinity is very precise and specific between a virus (famously diagrammed with its "spikes") and the host cell surface "binding receptor" (think of this as a key-and-lock match). This determines why some species are susceptible to a specific infection while others not at all. Another characteristic of viruses is their ability to mutate, which changes their genetic makeup. That can give them the ability to infect new hosts and alter the severity of the infection or its resistance to treatment.
Coronaviruses have been recognized since the 1960s as common causes of respiratory and gastrointestinal infections in humans and some other animals. Genetic studies have traced coronaviruses that coexisted with bats for millennia as a primary host but recently jumped to pangolins as new hosts and have now jumped to humans. What makes this human SARS-CoV2 (otherwise called COVID-19) much more dangerous to humans is its selective mutation to (1) bind to human receptor ACE2, which is abundant in our respiratory tract; and (2) to activate furin, a host-cell enzyme found in many human tissues (lungs, liver and small intestines), allowing the virus to increase its infectivity and attack multiple organs. Call this natural selection: Pure luck for the virus, bad karma for us?
So now, what about the Chinese connection? The first reports of novel pneumonia came from Wuhan, China. Why China first? One can only speculate that the Asian traditional obsession of consuming exotic animal tissues as medicinal remedies has invited importation of pathogens along with illegally trafficked animals. While not conclusive, most revealing is that both Chinese and Western scientists have found pangolins imported into Guangdong province contain coronaviruses with receptor binding properties identical to SARS-CoV2, potentially identifying pangolins as intermediate hosts to human disease.
It was an even more heartbreaking revelation for me as I watched the PBS "Nature" show on pangolins, documenting the effort of a few compassionate individuals who had tried, with little success, to stop the killing and trafficking of these adorable endangered creatures. Had the world listened to them, would this pandemic have ever occurred? Who knows, as so many "exotic" wild animals, including ferrets, are sold in open markets and pet stores around the world. Viruses don't recognize human skin colors nor nationalities; they only exploit human weaknesses or follies, wherever we are.
Zoonotic diseases are a group of infections that humans acquire from animal reservoirs. There are too many of them to list here. We need to remind ourselves that we live in a world where animal and human microbial cesspools are interconnected, ever-evolving, as humans encroach on wildlife habitat and contribute to climate change.
This COVID-19 pandemic is likely the mother of all zoonoses we have ever seen, now described as catastrophic or even apocalyptic. There have already been many stories written about it, and there surely will be many more: more scientific studies; stories of human tragedies, courage and immense sacrifices; of economic collapse; and of angry finger-pointing. Let's not forget the even larger, more existentialist lesson of how the wants, greed and follies of our human species can become our own peril, as we use our dominance to inflict cruelty over "lower" living species with whom we share — yes, share — this beautiful blue planet.
Chinh Le is a retired physician who lives in Corvallis.