Scientists are still investigating the origin of the coronavirus that has paralysed much of the planet.
Perhaps understandably, rumours have circulated that the virus might be man-made, but scientists have spoken out to explain why it’s not true, Science Alert has reported.
Specific features on the virus show that it’s the product of natural evolution, according to experts – and some of the features could not actually be made in a lab.
Earlier this year, research published in Nature also concluded that it was not man-made.
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Nigel McMillan, from the Menzies Health Institute Queensland, told Science Alert: "All evidence so far points to the fact the COVID-19 virus is naturally derived and not man-made.
"No system exists in the lab to make some of the changes found."
McMillan also pointed out that some of the features of the virus would simply not make sense if it had been designed by human beings.
McMillan said: "If you were going to design it in a lab the sequence changes make no sense as all previous evidence would tell you it would make the virus worse."
Rumours have also suggested that the virus may have originated in the Wuhan Institute of Virology (WIV), but researchers also said that this story doesn't entirely fit.
Edward Holmes, of the University of Sydney, said that the amount of changes in the virus kept in the WIV lab suggests it's unlikely to be the source.
Holmes said: "The closest known relative of SARS-CoV-2 is a bat virus named RaTG13, which was kept at the WIV. There is some unfounded speculation that this virus was the origin of SARS-CoV-2.
"However, RaTG13 was sampled from a different province of China (Yunnan) to where COVID-19 first appeared and the level of genome sequence divergence between SARS-CoV-2 and RaTG13 is equivalent to an average of 50 years (and at least 20 years) of evolutionary change."
Research also suggests another scenario where the virus has been circulating undetected for some time, possibly years.
The researchers wrote: "It is possible that a progenitor of SARS-CoV-2 jumped into humans” and acquired new features “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."
Coronaviruses are zoonotic, meaning they are transmitted between animals and people, the World Health Organization (WHO) says.
Coronaviruses are a large family of viruses that cause illnesses ranging from the common cold to more severe diseases such as Severe Acute Respiratory Syndrome (SARS).
The researchers suggest that it’s possible the virus could have “jumped” into humans many times, writing: “Sufficient opportunity could have arisen if there had been many prior zoonotic events that produced short chains of human-to-human transmission over an extended period.”
Researchers from the University of Minnesota investigated the “spike” protein on the surface of SARS-CoV-2 to understand why the virus spread so rapidly.
The work could lay the groundwork for drugs to block the novel coronavirus from attaching itself to, and infecting, human cells, the researchers believe.
The study was published in the journal Nature.
Professor Fang Li said: “In general, by learning what structural features of viral proteins are most important in establishing contact with human cells, we can design drugs that seek them out and block their activity like jamming their radar.
“Our work can guide the development of monoclonal antibodies that would act like a drug to recognise and neutralise the receptor-binding part of the spike protein.”