SUZHOU, China, Oct. 15, 2020 /PRNewswire/ -- Since the COVID-19 pandemic began, scientists have looked for an intermediate species that may have facilitated the jump of the coronavirus that causes the disease from bats – widely accepted as the origin – to humans.
Bats' physiology is relatively unlike that of humans, so scientists have considered a direct jump, or "zoonotic leap" unlikely – generally an animal virus needs to adapt to a human's body before infecting humans. Severe Acute Respiratory Syndrome (SARS) likely used civet cats in its path between bats and humans; Middle East Respiratory Syndrome (MERS) likely came from bats through camels to us.
However, a recent study implies the ancestors of the virus that causes COVID-19, SARS-CoV-2, may be predisposed to infect humans.
"After carefully removing the effects of recombination in the sarbecovirus genomes using sophisticated bioinformatics methods, our subsequent evolutionary analysis supports that this virus is likely the result of a direct or nearly direct zoonotic leap from bats," said Dr Xiaowei Jiang of Xi'an Jiaotong-Liverpool University's Department of Biological Sciences.
"'Nearly direct' means there is minimum evolution required for a SARS-CoV-2-like bat virus to jump to humans, which also implies the virus may be pre-adapted in bats to infect humans," he said.
"We found that a key genetic determinant on the spike protein of SARS-CoV-2, which determines the ability of the virus to infect human cells, appears to be ancestral and shared with bat viruses.
"That means the ability of SARS-CoV-2 to infect human cells may require minimum evolution or be pre-existing."
Dr Jiang is part of an international team of scientists from China, Europe and the U.S. responsible for the study "Evolutionary origins of the SARS-CoV-2 sarbecovirus lineage responsible for the COVID-19 pandemic," which was recently published in Nature Microbiology.
Dr Jiang said that the study indicates an urgent need for increased sampling in the viruses that gave rise to both SARS and COVID-19, the Sarbecovirus subgenus.
The viruses causing SARS and COVID-19 diverged decades (40-70 years) ago from existing coronaviruses, Dr Jiang said.
"The lineage that gave rise to the virus SARS-CoV-2 which caused COVID-19 has been circulating unnoticed in bats for decades," he said.
"This suggests a great deal of viral genetic diversity is not being sampled. Without these samples, we won't know the exact links between SARS, COVID-19 and future outbreaks."
Full paper: https://www.nature.com/articles/s41564-020-0771-4
