Staff at Temple University in Philadelphia, USA, have recreated the approximate genome of the progenitor SARS-CoV-2.
In order to understand how the virus spread and changed, you need to highlight its initial stages and study them. To do this, the researchers analyzed almost 1 million samples of the virus genome isolated from the body of COVID-19 carriers from January 2020 to the present day.
They reconstructed the evolutionary tree of the virus and compiled a genetic portrait of the common ancestor of all existing strains of SARS-CoV-2.
We have reconstructed the genome of the direct progenitor of SARS-CoV-2 using a huge database that contains over a million decoded coronavirus genomes. This analysis showed that by December 2019, the virus already had all the necessary tools to cause a worldwide epidemic.
Sudhir Kumar, professor at Temple University in Philadelphia
It turned out that the progenitor of the coronavirus was not completely identical in genome structure to the first strains of SARS-CoV-2. Also, there were no three small mutations in its genome, characteristic of most of the virus samples isolated from its first carriers in Wuhan.
Given the typical rate at which mutations appear in the genome of coronaviruses, the ancestor of the coronavirus began circulating through the human population around October 2019. This is about six to eight weeks before the first episode of its spread across China. He also already had all the features in order to spread widely across the Earth.