Researchers have identified a new coronavirus that is closely related to SARS-CoV-2, the virus behind COVID-19. The discovery provides fresh evidence that SARS-CoV-2 evolved naturally and was not produced in a lab. The new virus is not likely to infect humans.
Since the start of the coronavirus pandemic, rumors have circulated that the SARS-CoV-2 virus, which causes COVID-19, emerged from a laboratory in Wuhan, the city in China where the outbreak began.
This theory was recently given credence by United States President Donald Trump, who claimed to have evidence that SARS-CoV-2 originated in a Chinese laboratory. However, he has not shared any information that would support this claim.
Meanwhile, a growing body of scientific research strongly indicates that SARS-CoV-2 was not manufactured.
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New research published in the journal Current Biology adds to the evidence that the virus may have evolved naturally.
The team — led by researchers from Shandong First Medical University, in China — identified a new coronavirus in bats that is closely related to SARS-CoV-2. The two viruses are so closely related that it is highly unlikely that SARS-CoV-2 emerged from a laboratory.
The spike protein
Much of the debate about the origin of the novel coronavirus has centered on its spike protein, with which the virus binds to receptors on a host cell, ultimately allowing the virus to infect the cell and cause disease.
At the point where the two parts of the spike protein meet, there are an extra four amino acids, representing a difference from other coronaviruses. This feature, known as the S1/S2 insertion, is highly unusual and, so far, unique to SARS-CoV-2.
This unique characteristic of the spike protein has fuelled the idea that the virus may have been created in a laboratory.
“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,” elaborates senior author Prof. Weifeng Shi, director of the Institute of Pathogen Biology at the university.
A close relative
In order to compare the novel coronavirus to other, similar viruses, the researchers analyzed the genomes of 302 samples collected from 227 bats. The bats belonged to 20 different species.
The samples were collected from Yunnan province, in China, between May and October 2019 and sent for analysis in early January 2020, soon after SARS-CoV-2 was discovered.
Their genetic analysis identified a new coronavirus, called RmYN02, which has a very similar genome to SARS-CoV-2. The two viruses share 93.3% of their genetic information.
In some genetic regions, the new virus is even more similar than SARS-CoV-2’s current closest relative, RaTG13, which was also identified in bats from Yunnan.
In one of the longest parts of the genome that encodes for protein, RmYN02 shares 97.2% of its RNA with SARS-CoV-2.
Most importantly, according to the authors, RmYN02 has similar amino acid insertions in its spike protein, which suggests that these events — while highly unusual — occur naturally in evolution.
“Our paper shows very clearly that these events occur naturally in wildlife. This provides strong evidence against SARS-CoV-2 being a laboratory [escapee].”
– Prof. Weifeng Shi
The evolutionary ancestry of SARS-CoV-2
Although the insertions found in the new virus are not exactly the same as those in SARS-CoV-2, the fact that such similar genetic events have occurred in both viruses strongly suggests that they can occur naturally.
The team is hopeful that further investigations will identify other related viruses, eventually helping to explain exactly how SARS-CoV-2 made its way to humans.
“[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.”
– Prof. Weifeng Shi
It is important to note that the newly identified virus is not likely to infect humans. This is because it does not contain the same receptor-binding domain as SARS-CoV-2, which helps the latter infect human cells.
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