On May 10, in the journal Current Biology, researchers have listed an ancestral relative to SARS-CoV-2. This genome sequence is currently related to SARS-CoV-2 in terms of the amino acid insertions in the S1 and S2 junctions that spike up with similarities as that to SARS-CoV-2.
“Since the discovery of SARS-CoV-2, there have been a number of unfounded suggestions that the virus has a laboratory origin. In particular, it has been proposed the S1/S2 insertion is highly unusual and perhaps indicative of laboratory manipulation. Our paper shows very clearly that these events occur naturally in wildlife. This provides strong evidence against SARS-CoV-2 being a laboratory escape” says senior author Weifeng Shi, director and professor at the Institute of Pathogen Biology at Shandong First Medical University in China.
The new virus RmYN02 was identified in a 227 bat samples analysis that was from the Yunnan Province of China. These samples were collected from May to October 2019.
“Since the discovery that bats were the reservoir of SARS coronavirus in 2005, there has been great interest in bats as reservoir species for infectious diseases, particularly as they carry a very high diversity of RNA viruses, including coronaviruses,” says Shi.
Although the closest relative to this virus is actually RaTG13 across the whole genome sequence, which was previously identified from bats in Yunnan province as well, the new ancestor RmYN02 shares closer similarities than the previously identified ancestor. This one and SARS-CoV-2 seem to share 97.2% of the same RNA sequences as well as similar amino acid insertions within the genome sequence. These insertions have been identified as a common trait in all the SARS genome sequences, but even though the independent insertions between RmYN02 and SARS-CoV-2 aren’t exactly the same, they suffice as evidence to prove that the virus wasn’t made at a laboratory setup, but has occurred naturally.
Shi says that neither RaTG13 nor RmYN02 is the direct ancestor of SARS-CoV-2 because there is still an evolutionary gap between these viruses, but that their study strongly suggests that sampling of more wildlife species will reveal viruses that are even more closely related to SARS-CoV-2 and perhaps even its direct ancestors, which will tell a great deal about how this virus emerged in humans.