The study's title, "Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1", emphasizes that the study's authors compared the stability of the novel coronavirus to that of the original SARS virus.
The research was a collaborative, global effort: Andersen was joined by scientists from Columbia University in New York City, the University of Sydney in Australia, and Tulane University in New Orleans.
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The team acknowledged: "Although the evidence shows that SARS-CoV-2 is not a purposefully manipulated virus, it is now impossible to prove or disprove the other theories of its origin described here".
But Andersen's team believes their investigation proves otherwise.
Coronaviruses are a large family of viruses that can cause diseases that vary greatly in severity. In 2002 and 2003, the original SARS infected more than 8,000.
While both of those epidemics died out, COVID-19 continues to spread worldwide. However, the genetic data irrefutably show that SARS-CoV-2 is not derived from any previously used virus backbone.
Digging deeper, the researchers looked at the evolution of key components of the spike protein.
"It is improbable that SARS-CoV-2 emerged through laboratory manipulation of a related SARS-CoV-like coronavirus".
Now, scientists from Scripps Research say that the virus' origins come from natural selection. Just like many other respiratory viruses, including flu, Covid-19 can also spread in tiny droplets released from the nose and mouth while sneezing of an infected person.
The team concluded: "Irrespective of the exact mechanisms by which SARS-CoV-2 originated via natural selection, the ongoing surveillance of pneumonia in humans and other animals is clearly of utmost importance". The researchers said previous coronavirus outbreaks emerged in a similar way, with humans contracting the virus after direct exposure to civets (SARS), and camels (MERS). There are no documented cases of direct bat-human transmission, however, suggesting that an intermediate host was likely involved between bats and humans. A coronavirus from a pangolin could possibly have been transmitted to a human, either directly or through an intermediary host such as civets or ferrets. The distinct spike protein characteristic of SARS-CoV-2, the cleavage site, may have then evolved within a human host, possibly through limited undetected circulation in the human population prior to the beginning of the epidemic, the study said. This means that scientists still aren't sure why the novel coronavirus has become so much more widespread in comparison.
Reference: "The proximal origin of SARS-CoV-2" by Kristian G. Andersen, Andrew Rambaut, W. Ian Lipkin, Edward C. Holmes and Robert F. Garry, 17 March 2020, Nature Medicine.