SARS-CoV-2 ‘ready-made’ for human transmission, study suggests
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Toronto, Ontario (CTV News) — New research suggests that SARS-CoV-2, the virus that causes COVID-19, had already evolved to be able to infect humans prior to the first reported case, making the initial transmission from bats to humans an easy one.
The peer-reviewed research, published Friday in PLOS Biology, suggests that there was minimal significant genomic change to the virus until new variants began to take hold in different countries around the world.
“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,” Sergei Pond, professor at the Institute for Genomics and Evolutionary Medicine at Temple University, said in a press release.
The study analyzed over 100,000 genomes of the SARS-CoV-2 virus compared to 69 genomes of related Sarbecoviruses, the group of viruses that SARS-CoV-2 belongs to from bats and pangolins, looking for evolutionary changes that would show how the virus adapted to human transmission.
When doing further research of SARS-CoV-2 and the family of viruses it comes from, the researchers found that COVID-19 did at one point go through significant genomic changes, but that was before it made the jump to humans.
Researchers noted that because the virus was already able to transmit between species without major changes to its genomic structure, including between humans, minks, bats, cats, dogs, and other mammals, the data indicates that SARS-CoV-2 was already able to infect humans and other animals before the first human infection was documented.
Recent changes in the virus structure resulting in rapidly spreading variants, including B.1.1.7, B.1.351 and P.1, are a result of human-to-human transmission of the coronavirus, the study says.
“The reason for the ‘shifting of gears’ of SARS-CoV-2 in terms of its increased rate of evolution at the end of 2020, associated with more heavily mutated lineages, is because the immunological profile of the human population has changed,” David L. Robertson, professor at the MRC-University of Glasgow Centre for Virus Research, said in the release.
Virus variants work to evade antibodies and immunities that humans have picked up, and the authors of the study say these new variants are moving further away from the early 2020 variant used to make vaccines.
“The first race was to develop a vaccine. The race now is to get the global population vaccinated as quickly as possible,” Robertson said.
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