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Opinion | The Pandemic, from the Coronavirus’s Perspective

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 those reservoir hosts may prepare the viruses nicely for infecting us.

The closest known relative of SARS-CoV-2 is a virus discovered seven 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 percent similar to SARS-CoV-2, but that four percentage point difference represents decades of evolutionary divergence, possibly in a different population 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.

What happened, during those decades of evolutionary divergence, to bring a still-undiscovered bat coronavirus to the brink of spillover into humans and enable it to become SARS-CoV-2? We don’t yet know. Scientists in China will keep looking for that closer-match virus. The evidence gathered so far is mixed and incomplete, complicated by the fact that coronaviruses are capable of a nifty evolutionary trick: recombination.

That means that when two strains of coronavirus infect the same individual animal, they may swap sections and emerge as a composite, possibly (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 Homo sapiens.

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 imperative 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 travails of this Covid-19 emergency? Yes.

Dr. Morens has recently been a co-author of another paper examining how coronaviruses have come at us. In it, he and his colleagues nod to the eminent molecular biologist Joshua Lederberg, a Nobel Prize laureate in 1958, at age 33, who later wrote: “The future of humanity and microbes likely will unfold as episodes of a suspense thriller that could be titled ‘Our Wits Versus Their Genes.’ ”

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