covid-19 Corona virus epidemic occurs naturally, scientists say
Electron micrograph of COVID-19 corona virus. Scripps Research’s analysis of open genome sequence data for SARS-CoV-2 and related viruses did not find any evidence that the virus was made in the lab or otherwise.
The novel SARS-CoV-2 coronavirus, which has spread to more than 70 different countries since the outbreak in Wuhan, China last year, caused a massive COVID-19 epidemic, is a product of natural evolution. Journal of Natural Medicine.
Analysis of open genomic sequence data of SARS-CoV-2 and related viruses has not found any evidence that the virus has been created in a laboratory or otherwise.
Dr. Christian Andersen, Associate Professor of Immunology and Microbiology at Scripps Research, said, “By comparing the available genomic sequence data for known corona virus strains, we can be sure that SARS-CoV-2 was produced through natural processes.” said . paper.
In addition to Andersen, the author of the paper, “The Proximal Origin of SARS-CoV-2,” includes Robert F. Garry of Tulane University; Edward Holmes at the University of Sydney; Andrew Rambaut of the University of Edinburgh; Columbia University’s W. Ian Lipkin.
Corona virus is a large group of viruses that can cause a wide range of diseases. The first serious illness caused by the corona virus appeared in China in 2003 as a serious acute respiratory syndrome (SARS) epidemic. The second outbreak of severe disease began in Saudi Arabia in 2012 with Middle East Respiratory Syndrome (MERS).
A, mutation at the contact residue of SARS-CoV-2 spike protein. The spike protein of SARS-CoV-2 (red bar at the top) was aligned against the most closely related SARS-CoV-like corona virus and SARS-CoV itself. The main residue of the spike protein in contact with the ACE2 receptor is blue in both related viruses, including SARS-CoV-2 and SARS-CoV (Urbanii strain).
Characters. b, Acquisition of polybasic cleavage sites and O-linked glycans. The polybasic cleavage site and three adjacent predicted O-linked glycans are unique to SARS-CoV-2 and have not been previously seen in the lineage B beta corona virus. Sequences shown are from NCBI GenBank, accession codes MN908947, MN996532, AY278741, KY417146 and MK211376.
On December 31, last year, Chinese authorities warned the World Health Organization (WHO) that a new strain of coronavirus that caused serious illness has occurred. As of February 20, 2020, nearly 167,500 COVID-19 cases have been reported, but it seems that the milder cases have not been diagnosed. The virus killed more than 6,600 people.
Shortly after the epidemic began, Chinese scientists sequenced the genome of SARS-CoV-2 and provided data to researchers around the world. The resulting genomic sequence data showed that Chinese authorities quickly detected the epidemic and that the number of COVID-19 cases increased due to human-to-human transmission after a single introduction into the human population. Andersen and collaborators from several other laboratories used this sequencing data to explore the origins and evolution of SARS-CoV-2, focusing on the different characteristics of the virus.
Scientists analyzed genetic templates for spike proteins, bones outside the virus, used to grab and penetrate the outer walls of human and animal cells. More specifically, they focused on two important characteristics of the spike protein: the receptor-binding domain (RBD), a type of grappling hook that hangs on the host cell, and the cleavage site, a molecular opening that allows the virus to crack. Then enter the host cell.
Evidence for natural evolution
Scientists have discovered that the RBD portion of the SARS-CoV-2 spike protein has evolved to effectively target molecular features outside of human cells called ACE2, a receptor involved in blood pressure regulation. The SARS-CoV-2 spike protein is very effective at binding to human cells, so scientists have concluded that this is not a product of genetic engineering, but a result of natural selection.
This evidence for natural evolution was supported by data on the backbone (full molecular structure) of SARS-CoV-2. If someone wanted to design a new corona virus as a pathogen, it would have made it from the backbone of a virus known to cause disease. However, scientists have found that the SARS-CoV-2 backbone is substantially different from the known corona virus and is similar to the related virus found mostly in bats and pangolines.
“These two characteristics of the virus, the mutation in the RBD portion of the spike protein and the distinct skeleton, exclude laboratory manipulation as a potential source of SARS-CoV-2,” said Andersen.
Dr. Josie Golding, director of epidemics at the Wellcome Trust in the UK, found that Andersen and his colleagues found it crucial to present evidence-based views of the rumors spread about the origins of the virus As important as (SARS-CoV -2) the cause of COVID-19 ”
“They concluded that the virus was the product of natural evolution,” Godding added. “The guess about deliberate genetic engineering is over.”
Possible origins of the virus
Based on their genome sequencing analysis, Andersen and his collaborators concluded that the origin of SARS-CoV-2 followed one of two possible scenarios.
In one scenario, the virus evolved into a current pathogenic state through natural selection in a non-human host and then plunged into humans. This is how the previous coronavirus occurred as a person contracted with the virus after being directly exposed to musk (SARS) and camels (MERS). Researchers suggested bats as the best reservoir for SARS-CoV-2, because they are very similar to the bat corona virus. However, although direct cases of bat-to-human transmission have not been documented, it is likely that an intermediate host was involved between bats and humans.
In this scenario, the unique characteristics of the spike protein of SARS-CoV-2 (the portion of the RBD that binds to the cell and the cleavage site that opens the virus) would all have evolved to its present state before entering humans. In this case, since the virus is already pathogenic and has already evolved the ability to spread among people, the current epidemic would have appeared rapidly as soon as a person became infected.
In another proposed scenario, the non-pathogenic virus version jumped from animal host to human and evolved to the current pathogenic state within the human population. For example, some coronaviruses from pangolins, armadillo-like mammals found in Asia and Africa, have RBD structures very similar to SARS-CoV-2. Coronaviruses from pangolins may have been transmitted to humans either directly or through intermediary hosts such as musk or ferrets.
Then, other distinct spike protein properties of the cleavage site SARS-CoV-2 may have evolved within the human host through circulation that was not limitedly detected in the human population before the onset of the epidemic. The researchers found that the SARS-CoV-2 cleavage site appeared similar to that of the avian influenza strain, which is easily transmitted from person to person. SARS-CoV-2 has begun the current epidemic by evolving these toxic divisions in human cells because the corona virus could spread much more between humans.
Research co-author Andrew Lambout warned that it is not impossible to know which scenario is most likely at this point. When SARS-CoV-2 enters humans in the current pathogenic form from a zoo, the disease-causing strains of the virus still circulate in the animal population and can once again increase the likelihood of future development. human. Nonpathogenic coronaviruses are unlikely to enter a human population and then develop characteristics similar to SARS-CoV-2.