You’ve heard the conspiracy theories: The coronavirus SARS-CoV-2 now sweeping the world was created in a lab in Wuhan, China.
“Don’t buy China’s story: The coronavirus may have leaked from a lab,” The New York Post wrote back on Feb. 11.
The story says Chinese leader Xi Jinping “didn’t actually admit that the coronavirus now devastating large swaths of China had escaped from one of the country’s bioresearch labs. But the very next day, evidence emerged suggesting that this is exactly what happened, as the Chinese Ministry of Science and Technology released a new directive titled: ‘Instructions on strengthening biosecurity management in microbiology labs that handle advanced viruses like the novel coronavirus.’ …
It turns out that in all of China, there is only one. And this one is located in the Chinese city of Wuhan that just happens to be … the epicenter of the epidemic. That’s right. China’s only Level 4 microbiology lab that is equipped to handle deadly coronaviruses, called the National Biosafety Laboratory, is part of the Wuhan Institute of Virology.
That rumor spread even more quickly than the virus itself.
But a new analysis of SARS-CoV-2 should end that conspiracy theory, a group of researchers say. They compared the genome of the new coronavirus with the seven other coronaviruses known to infect humans and drew a clear conclusion: “Our analyses clearly show that SARS-CoV-2 is not a laboratory construct or a purposefully manipulated virus,” they wrote in the journal Nature Medicine.
The researchers compared SARS, MERS and SARS-CoV-2, HKU1, NL63, OC43 and 229E and compared the receptor-binding domain (RBD) and how it binds with receptors called ACE-2 (to be highly technical, ACE-2 is a type I transmembrane metallocarboxypeptidase with homology to ACE).
“The RBD of SARS-CoV-2 is optimized for binding to human ACE2 with an efficient solution different from those previously predicted. Furthermore, if genetic manipulation had been performed, one of the several reverse-genetic systems available for betacoronaviruses would probably have been used. However, the genetic data irrefutably show that SARS-CoV-2 is not derived from any previously used virus backbone,” the researchers wrote.
Instead, they offer two scenarios that can explain the origin of SARS-CoV-2: “natural selection in an animal host before zoonotic transfer; and … natural selection in humans following zoonotic transfer.”
As many early cases of COVID-19 were linked to the Huanan market in Wuhan, it is possible that an animal source was present at this location. Given the similarity of SARS-CoV-2 to bat SARS-CoV-like coronaviruses2, it is likely that bats serve as reservoir hosts for its progenitor. Although RaTG13, sampled from a Rhinolophus affinis bat, is ~96% identical overall to SARS-CoV-2, its spike diverges in the RBD, which suggests that it may not bind efficiently to human ACE2. …
It is possible that a progenitor of SARS-CoV-2 jumped into humans, acquiring the genomic features described above through adaptation during undetected human-to-human transmission. Once acquired, these adaptations would enable the pandemic to take off and produce a sufficiently large cluster of cases to trigger the surveillance system that detected it.
“The overall molecular structure of this virus is distinct from the known coronaviruses and instead most closely resembles viruses found in bats and pangolins that had been little studied and never known to cause humans any harm,” the researchers write.
“If someone were seeking to engineer a new coronavirus as a pathogen, they would have constructed it from the backbone of a virus known to cause illness,” according to a statement from Scripps Research. ” If someone were seeking to engineer a new coronavirus as a pathogen, they would have constructed it from the backbone of a virus known to cause illness. But the scientists found that the SARS-CoV-2 backbone differed substantially from those of already known coronaviruses and mostly resembled related viruses found in bats and pangolins.”
“These two features of the virus, the mutations in the RBD portion of the spike protein and its distinct backbone, rules out laboratory manipulation as a potential origin for SARS-CoV-2,” said Kristian Andersen, an associate professor of immunology and microbiology at Scripps Research and corresponding author on the paper.