The novel SARS-CoV-2 coronavirus that emerged in the city of Wuhan, China, in December 2019 and has since caused the CoVID-19 pandemic, spreading to 170 countries and regions, is the product of natural evolution, according to findings published by scientists from the United States, United Kingdom, and Australia in Nature Medicine. The analysis of public genomic cequence data from SARS-CoV-2 and related viruses found no evidence that the virus was made in a laboratory or otherwise engineered.
Shortly after the epidemic began, Chinese scientists sequenced the genome of SARS-CoV-2 and made the data available to researchers worldwide. The sequence data showed that the number of COVID-19 cases increased because of human to human transmission after a single introduction into the human population. The scientists then analyzed the genetic template for spike proteins, structures outside of the virus that it uses to grab and penetrate the outer walls of human and animal cells. They examined the two important features of the spike protein, the receptor-binding domain (RBD), a kind of grappling hook that grips onto host cells, and the cleavage site, a molecular can opener that allows the virus to crack open and enter host cells.
The scientists found that the RBD portion of the SARS-CoV-2 spike proteins evolved to effectively target a molecular feature on the outside of human cells called ACE2, a receptor involved in regulating blood pressure. The SARS-CoV-2 spike protein was so effective at binding the human cells, in fact, that the scientists concluded it was the result of natural selection and not the product of genetic engineering.
Coronaviruses are a large family of viruses that can cause 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 second outbreak of severe illness began in 2012 in Saudi Arabia with the Middle East Respiratory Syndrome (MERS). The Johns Hopkins Coronavirus Resource Center reports 422,989 COVID-19 cases as of March 25, 2020, with 18,916 deaths and 108,578 recoveries.