SARS-CoV-2 began to actively spread 6-8 weeks before detection in Wuhan

In order to understand how the virus spread and changed, it is necessary to identify its initial stages and

study them. To do this, 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 directthe 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 notcompletely 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.

If we take into account the typical rate of occurrence of mutations ingenome of coronaviruses, its ancestor began circulating throughout the human population around October 2019. This is about six to eight weeks before the first episode of its spread across China begins. Also, it already had all the features to spread widely across the Earth. 

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