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Coronavirus Was Circulating Two Months Before COVID-19 Cases Reported in China

The research, published in the journal Science, used molecular dating tools and epidemiological simulations to date the emergence of the virus to as early as October 2019.The researchers used molecular clock evolutionary analyses to try to home in on when the first or index, case of SARS-CoV-2 occurred.

"The index case can conceivably predate the common ancestor - the actual first case of this outbreak may have occurred days, weeks or even many months before the estimated common ancestor," said study co-author Michael Worobey, a professor at the University of Arizona.