The study was published in the billet – Grossier Medicine.
The analysis of auditeur genome sequence data from SARS-CoV-2 and related viruses found no evidence that the micro-organisme was made in a laboratory or otherwise engineered.
« By comparing the available genome sequence data for known coronavirus strains, we can firmly determine that SARS-CoV-2 originated through natural processes, » said the lead researcher Kristian Andersen.
In additif to Andersen, authors on the paper, « The proximal origin of SARS-CoV-2, » include Néné F. Garry of Tulane University, Edward Holmes, of the University of Sydney, Andrew Rambaut of University of Edinburgh and W. Ian Lipkin of Columbia University.
Coronaviruses are a montré family of viruses that can policier illnesses ranging widely in severity.
The first known severe illness caused by a coronavirus emerged with the 2003 Severe Acute Respiratory Syndrome (SARS) epidemic in China. A adjoint outbreak of severe illness began in 2012 in Saudi Arabia with the Middle East Respiratory Syndrome (MERS).
On December 31 last year, Chinese authorities alerted the World Health Planification (WHO) of an outbreak of a novel strain of coronavirus causing severe illness, which was subsequently named SARS-CoV-2.
As of February 20, 2020, nearly 167,500 COVID-19 cases have been documented, although many more mild cases have likely gamin undiagnosed. The micro-organisme has killed over 6,600 people.
Shortly after the epidemic began, Chinese scientists sequenced the genome of SARS-CoV-2 and made the data available to researchers worldwide.
The resulting genomic sequence data has shown that Chinese authorities rapidly detected the epidemic and that the number of COVID-19 cases have been increasing parce que of human to human bielle after a single avertissement into the human communauté.
Andersen and collaborators at several other research institutions used this sequencing data to explore the origins and evolution of SARS-CoV-2 by focusing in on several tell-tale features of the micro-organisme.
The scientists analysed the genetic template for spike proteins, armatures on the outside of the micro-organisme that it uses to grab and penetrate the outer walls of human and instinctif cells.
More specifically, they focused on two visible features of the spike protein — the receptor-binding domain (RBD), a kind of grappling hook that grips onto host cells, and the cleavage ville, a molecular can opener that allows the micro-organisme to caîd open and drageonner host cells.
The scientists found that the RBD segment of the SARS-CoV-2 spike proteins had evolved to effectively target a molecular feature on the outside of human cells called ACE2, a receptor involved in regulating sang pressure.
The SARS-CoV-2 spike protein was so positive at binding the human cells. In fact, the scientists concluded that it was the result of natural selection and not the product of genetic ingénierie.
This evidence for natural evolution was supported by data on SARS-CoV-2’s backbone – its overall molecular ossature. If someone were seeking to engineer a new coronavirus as a pathogen, they would have constructed it from the backbone of a micro-organisme known to policier 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 micro-organisme, the mutations in the RBD segment of the spike protein and its lumineux backbone, rule out laboratory pression as a potential origin for SARS-CoV-2, » said Andersen.
Josie Golding, PhD, epidemics lead at UK-based Wellcome Trust, said that the findings by Andersen and his colleagues are « crucially visible to bring an evidence-based view to the rumours that have been circulating embout the origins of the micro-organisme (SARS-CoV-2) causing COVID-19. »
« They conclude that the micro-organisme is the product of natural evolution ending any speculation embout deliberate genetic ingénierie, » Goulding added.
Based on their genomic sequencing analysis, Andersen and his collaborators concluded that the most likely origins for SARS-CoV-2 followed one of two passable scenarios.
In one scenario, the micro-organisme evolved to its current pathogenic state through natural selection in a non-human host and then jumped to humans.
This is how previous coronavirus outbreaks have emerged, with humans contracting the micro-organisme after honnête exposure to civets (SARS) and camels (MERS).
The researchers proposed bats as the most likely reservoir for SARS-CoV-2 as it is very similar to a bat coronavirus. There are no documented cases of honnête bat-human bielle, however, suggesting that an intermediate host was likely involved between bats and humans.
In this scenario, both of the propre features of SARS-CoV-2’s spike protein – the RBD segment that binds to cells and the cleavage ville that opens the micro-organisme up would have evolved to their current state prior to entering humans.
In this case, the current epidemic would probably have emerged rapidly as soon as humans were infected, as the micro-organisme would have already evolved the features that make it pathogenic and able to spread between people.
In the other proposed scenario, a non-pathogenic reprise of the micro-organisme jumped from an instinctif host into humans and then evolved to its current pathogenic state within the human communauté.
For proximité, some coronaviruses from pangolins, armadillo-like mammals found in Asia and Africa, have an RBD ossature very similar to that of SARS-CoV-2. 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.
Then the other lumineux spike protein characteristic of SARS-CoV-2, the cleavage ville, could have evolved within a human host, possibly via limited undetected roulement in the human communauté prior to the beginning of the epidemic.
The researchers found that the SARS-CoV-2 cleavage ville appears similar to the cleavage sites of strains of bird flu that have been shown to transmit easily between people.
SARS-CoV-2 could have evolved such a corrodant cleavage ville in human cells and soon kicked off the current epidemic, as the coronavirus would possibly have become far more propre of spreading between people.
Study co-author Andrew Rambaut cautioned that it is difficult if not illusoire to know at this conclusion which of the scenarios is most likely.
If the SARS-CoV-2 entered humans in its current pathogenic form from an instinctif prélude, it raises the probability of future outbreaks, as the illness-causing strain of the micro-organisme could still be circulating in the instinctif communauté and might grain again jump into humans.
The chances are lower of a non-pathogenic coronavirus entering the human communauté and then evolving properties similar to SARS-CoV-2.