COVID-19 from the virus’s point of view
Covid-19: Consider the Virus’s Point of View
No sensible person can dispute the Covid-19 is a great tragedy for humanity. Although deadly viruses are around us all the time, our treatment of this disease has brought disaster upon ourselves. The scope and devastation of the pandemic reflect bad luck, yes, and a dangerous world, yes, but also catastrophic failures of human foresight, communal will and leadership.
But look past that record of human failures for a moment and consider this whole event from the point of view of the virus. Measure it by the cold logic of evolution. The career of SARS-CoV-2 so far, is, in Darwinian terms, a great success story.
This now-notorious coronavirus was once an inconspicuous creature, lurking quietly in its natural host: some population of animals, possibly bats, in the caves and remnant forests of southern China. The existence of such a living hide-out—also known as a reservoir host—is logically necessary when any new virus appears suddenly as a human infection.
Why? Because everything comes from somewhere, and viruses come from cellular creatures such as animals, plants or fungi. (A viral particle isn’t a cell; it’s just a strip of genomic instructions enclosed in a protein capsule—a message in a bottle.) A virus can only replicate itself, function as though it were alive and exist over time if it inhabits the cells of a more complex creature, like a sort of genetic parasite.
Generally, this relationship between virus and reservoir host represents an ancient evolutionary accommodation. The virus persists at a low profile, without causing trouble, without proliferating explosively, and in return it gets long term security. Its horizons are modest: relatively small population, limited geographical scope.
But this guest-host arrangement is not always stable, or the end of the story. If another sort of creature comes in close contact with the host—by preying on it, by capturing it or maybe only by sharing the same cave—this virus might be shaken from its comfort zone and into a new situation; a potential new host.
Suddenly it’s like a gaggle of rats that jump ashore from a ship onto a remote island. The virus might thrive in this new habitat, or it may fail and die out. If it happens to thrive, if by chance it finds the new situation hospitable, then it might establish itself not just in the first new individual, but in the new population.
It might discover itself capable of entering some of the new host’s cells, replicating abundantly and getting itself transmitted from that individual to others. That jump is called host-switching or, by a slightly more vivid term spillover. If the spillover results in disease among a dozen or two dozen people, you have an outbreak. If it spreads countrywide, an epidemic, worldwide, a pandemic.
Imagine again that gaggle of rats on a previously rat-free island. To their delight, they find the island inhabited by several endemic species of birds, naïve and trusting, accustomed to laying their eggs on the ground. The rats eat those eggs. Soon the island has lost most of its endemic species of birds, but it has an abundance of rats.
Over time, the rats acquire the ability to dig lizards out of their hiding places amid rocks and logs and eat them. They develop an improved agility at tree climbing and eat eggs from bird’s nests up there, too. Now, you might as well call the place Rat Island. For the rats, this is a tale of evolutionary success.
If the remote island of habitat is a human being newly colonized by a virus from a nonhuman animal, we call that virus a zoonosis. The resulting infection is a zoonotic disease. More than6 0 per cent of human infectious diseases, including COVID-19 fall into this category of zoonosis that have succeeded. Some zoonotic diseases are caused by bacteria (such as the bacillus responsible for the bubonic plague) or other kinds of pathogens but most are viral.
Viruses have no malic against us. They have no purposes, no schemes. They follow the same Darwinian imperatives as do rats or any other creature driven by genome: to extend themselves as much as possible in abundance, in geographical space and in time. Their primal instinct was described in Geneses 1:28 when God said, “Be fruitful and multiply and fill the earth, and subdue it.”
For an obscure virus, living in its reservoir host—a bat or a monkey in some remote region of Asia or Africa, or maybe a mouse in the American southwest—spilling over into humans offers the opportunity to comply. Not every successful virus will “subdue” the planet, but some go a fair way to toward subduing at least humans.
This how the AIDS epidemic happened. A chimpanzee virus now known as SIVcpz passed from a single chimp into a single human, possibly by blood contact during mortal combat and took hold in a human. Molecular evidence developed by two teams of scientists, one lead by Dr. Beatrice Hahn, the other by Michael Worobey, tells us that this most likely happened more than a century ago in the southwest corner of Cameroon, in Central Africa, and that the virus took decades to attain proficiency at human-to-human transmission.
By 1960 that virus had travelled downriver to big cities such as Kinshasa, the capital of the Democratic Republic of Congo; then it spread to the Americas and burst into notice in the 1980’s. Now we call it “H.I.V.-1ggroup M”: It’s the pandemic strain, accounting for most of the 71 million human infections to date.
Chimpanzees were a species in decline because of habitat loss and killing by humans; humans were a species in ascendance. The SIVcpz virus reversed its own evolutionary prospects by getting into us and adapting well to the new host. It jumped from a sinking boat onto a luxury cruise ship.
SARS-CoV-2 has done likewise, though its success has occurred much more quickly. It has now infected more than 37 million people, more than half as many as the number infected by H.I.V. and in 10 months rather than ten decades. It’s not the most successful human-infecting virus on the planet—that distinction lies elsewhere possible with the Epstein-Barr virus, a very transmissible species of herpesvirus, which may reside within a least 90 per cent of all humans, causing syndromes in some and lying latent in most. But SARS-CoV-2 is off to a roaring start.
Now, for purposes of illustration, imagine a different scenario, involving a different virus. In the mountain forests of Rwanda lives a small, insectivorous bat know as Hill’s horseshoe bat. This bat is real but is has been seen only rarely and has been classified as a critically endangered species. There is a virus living in the bat which this virus uses as its reservoir host. We will call it RhRW19 a coded abbreviation that shows the bat was from Rwanda and found in 2019.
The virus is hypothetical, but it’s possible, given that coronaviruses are known to occur in many kinds of horseshoe bats around the world. RhRW19 is on the brink of extinction, because the rare bat is its sole refuge. The lifeboat is leaking badly and sinking.
But then a single Rwandan farmer needing fertilizer for his crops on a meager patch of dirt enters a cave and shovels up some bat guano. The guano has come from Hill’s horseshoe bats and it contains the virus. In the process of shoveling and breathing, the farmer becomes infected with EhRW19. He passes it to his brother, and the brother carries it to a provincial clinic where he works as a nurse. The virus circulates for weeks among employees at the clinic and their contacts, making some sick, killing one person, while natural selection improves its capacity to replicate within cells of the human respiratory tract and transmit between people.
A vising doctor becomes infected and she carries the virus back to Kigali, the capital. Soon it is at the airport, in the airways of people who don’t yet feel symptoms and are boarding flights for Kinshasa, Doha and London. Now you can give the improved virus a different name: SARS-CoV-3. It’s a success story that hasn’t happened but yet very easily could.
Coronaviruses are an exceptionally dangerous group. The Journal Cell recently published a paper on pandemic diseases and how COVID-19 has come upon us, by a scientist names Dr.David M. Morens, who also serves as senior scientific advisor to the director of the National Institute of Allergy and Infectious diseases, Dr. Anthony Fauci. Dr. Fauci co-authored his paper.
The paper says, among other things, that coronaviruses harbored in various mammalian species “may essentially be preadapted to human infectivity.” Not just bats but other mammals—pangolins, palm civets, cats, ferrets, mink, who knows what—contain cells that are susceptible to the same viral hooks that allow coronaviruses to catch hold of some human cells. Existing within these reservoir hosts may prepare the viruses nicely for infecting us.
The closest known relative of SARS-CoV-2 is a virus discovered 7 years ago, in a bat captured at a mine shaft in Yunnan Province, China by a team under the leadership of Dr. Zhengli Shi, of the Wuhan Institute of Virology. This virus carries the moniker RaTG13. It is about 96 per cent similar to SARS-CoV-2 but that four percentage point difference represents decades of evolutionary divergence, possible in different populations of bats. In other words, RaTG13 and our nemesis bug are not the same virus; they are like cousins who have lived all their adult lives in separate towns.
That means when two separate strains of coronavirus infect the same individual animal, they may swap sections and emerge as a composite, possible (by sheer chance) encompassing the most aggressive, adaptive sections of the two. SARS-CoV-2 may be such a composite, built by happenstance and natural selection from components known to exist among other viruses in the wild, and emerging from its nonhuman host with a fearsome capacity to grab, enter and replicate within certain human cells Bad luck for us. But evolution is not rigged to please the human race.
SARS-CoV-2 has made a great career move, spilling over from its reservoir host into humans. It already has achieved two of the three Darwinian imperatives: expanding its abundance and extending its geographical range. Only the third remains as a challenge” to perpetuate itself in time.
Will we ever be rid of it entirely, now that it’s a human virus? Probably not. Will we ever get past the horrors of this world-wide pandemic? Yes.
The future of humanity and microbes is like an ongoing suspense novel with humans matching wits against invading organisms. So far, our intelligence has won out and we will survive this virus and go on.
And yet, in a strange way, without deadly viruses, floods, draughts, famine, disease and wars, this planet may have been overpopulated hundreds of years ago. Maybe there is a plan to keep this planet intact and viruses are part of that plan, but we just don’t know about it.