COVID VIRUS JUMPED FROM BATS TO HUMANS WITHOUT MUCH CHANGE: STUDY

An article published in the open-access journal PLOS Biology and written by Oscar MacLean, Spyros Lytras at the University of Glasgow, and their colleagues showed that since December 2019 and for the first 11 months of the SARS-CoV-2 pandemic, there has been very little 'important' genetic change observed in the hundreds of thousands of sequenced virus genomes.

The study is a collaboration of researchers in the United Kingdom, United States, and Belgium. The lead authors Prof. David L Robertson (at the MRC-University of Glasgow Center for Virus Research, Scotland) and Prof Sergei Pond (at the Institute for Genomics and Evolutionary Medicine, Temple University, Philadelphia) were able to turn their experience of analyzing data from HIV and other viruses to SARS-CoV-2.

Pond's state-of-the-art analytical framework, HyPhy, was instrumental in teasing out the signatures of evolution embedded in the virus genomes and rests on decades of theoretical knowledge on molecular evolutionary processes.

First author Dr. Oscar MacLean explains: "This does not mean no changes have occurred, mutations of no evolutionary significance accumulate and 'surf' along the millions of transmission events like they do in all viruses."

Some changes can affect; for example, the Spike replacement D614G which has been found to enhance transmissibility, and certain other tweaks of virus biology scattered over its genome. On the whole, though, 'neutral' evolutionary processes have dominated.

MacLean adds "this stasis can be attributed to the highly susceptible nature of the human population to this new pathogen, with limited pressure from population immunity, and lack of containment, leading to exponential growth making almost every virus a winner."

Pond comments "what's been so surprising is just how transmissible SARS-CoV-2 has been from the outset.

Usually, viruses that jump to a new host species take some time to acquire adaptations to be as capable as SARS-CoV-2 at spreading, and most never make it past that stage, resulting in dead-end spillovers or localized outbreaks."

Studying the mutational processes of SARS-CoV-2 and related sarbecoviruses (the group of viruses SARS-CoV-2 belongs to bats and pangolins), the authors find evidence of fairly significant change, but all before the emergence of SARS-CoV-2 in humans.

This means that the “generalist” nature of many coronaviruses and their apparent facility to jump between hosts, imbued SARS-CoV-2 with ready-made ability to infect humans and other mammals, but those properties most have probably evolved in bats prior to spillover to humans.

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