The COVID-19 virus may have resulted from coronaviruses in bats and pangolins exchanging their genetic materials, Gao Feng, an infectious disease expert affiliated with Jilin University in northeastern China and Duke University in the U.S., told Sixth Tone on Monday.
Current evidence suggests that SARS-CoV-2, the coronavirus that causes COVID-19, likely came from bats because of genetic similarities between it and a coronavirus found in certain populations of the flying mammals. However, how the bat virus evolved to infect humans remains a mystery, given that it lacks a key structure found in SARS-CoV-2 for binding effectively to human cells.
Gao and his colleagues may have discovered a clue after comparing 43 genetic sequences in coronaviruses from bats, pangolins (a type of scaly anteater), and COVID-19 patients.
According to a study published Friday in the peer-reviewed journal Science Advances, the team found that the part of the SARS-CoV-2 gene coding for the critical viral structure used to invade human cells was highly similar to that of a pangolin coronavirus.
The rest of SARS-CoV-2, however, was significantly more similar to a bat coronavirus. To the researchers, this suggested that coronaviruses in bats and pangolins might have exchanged their genetic materials at some point via a process called recombination, giving rise to SARS-CoV-2.
Genetic recombination in nature happens when different viruses encounter each other, usually in hosts. They swap some of their genetic materials, and this sometimes leads to the emergence of new viruses.
“Recombination between viruses is very common,” Gao said. “It’s an important strategy viruses use to gain new traits that help them survive better.”
But where the exchange occurred remains unknown, and pangolins may not be the intermediate host — the missing link between bats and humans.
“This is a black box. The recombination may have occurred after bats spread their virus to pangolins, or pangolins gave their virus to bats, from which it then jumped to some other animals,” Gao said. “We don’t have enough animal samples to reach a definitive conclusion yet.”
According to Gao, the coronaviruses that caused SARS, MERS, and COVID-19 — three major coronavirus disease outbreaks in humans — were all linked to genetic recombination between bats and other animals. Wet markets that house a variety of wild animals in close proximity provide a conducive environment for genetic reshuffling, and could lead to the emergence of more infectious viruses, Gao said.
“While the direct reservoir of SARS-CoV-2 is still being sought, one thing is clear: reducing or eliminating direct human contact with wild animals is critical to preventing new coronavirus zoonosis in the future,” the authors wrote in their paper.
Editor: David Paulk.
(Header image: A pangolin secured with a rope is displayed in a residential area of Chongqing, May 3, 2020. IC)