One of the persistent conspiracy theories around the coronavirus has been that the virus is man-made.
A new study has offered further evidence that this is untrue.
The research, published in Current Biology, has identified a bat coronavirus that is among the closest relatives of the novel coronavirus currently ravaging the world.
Importantly, the newly-found virus includes unusual features in its spike protein, which some had suggested as evidence that the virus was man-made.
The find could lead to viruses that are direct ancestors of the novel coronavirus (SARS-CoV-2), which could help us understand how it first infected humans, the researchers said.
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Senior author Weifeng Shi, director and professor at the Institute of Pathogen Biology at Shandong First Medical University in China, said: “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."
The new virus is not a direct evolutionary precursor of SARS-CoV-2.
The discovery of the new virus, RmYN02, suggests that these types of seemingly unusual insertion events can occur naturally in coronavirus evolution, the researchers said.
The closest relative to SARS-CoV-2 is another virus, called RaTG13, which was previously identified from bats in Yunnan province.
But RmYN02, the virus newly discovered here, is even more closely related to SARS-CoV-2 in some parts of the genome, including in the longest encoding section of the genome called 1ab, where they share 97.2% of their RNA (ribonucleic acid).
The researchers noted that RmYN02 did not closely resemble SAR-CoV-2 in the region of the genome that encodes the key receptor binding domain that binds to the human ACE2 receptor that SARS-CoV-2 uses to infect host cells.
This means it's not likely to infect human cells.
“Our findings suggest that these insertion events that initially appeared to be very unusual can, in fact, occur naturally in animal betacoronaviruses,” Shi said.
"Our work sheds more light on the evolutionary ancestry of SARS-CoV-2," he added. "Neither RaTG13 nor RmYN02 is the direct ancestor of SARS-CoV-2, because there is still an evolutionary gap between these viruses.
“But our 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 us a great deal about how this virus emerged in humans."