Figure 1.

The divergence of coronaviruses into Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus is estimated to have occurred approximately 5000 years ago. This tree was generated by analyzing RNA-dependent RNA polymerase (RdRp) genes under the relaxed-clock model with an uncorrelated log-normal distribution in Bayesian evolutionary analysis sampling trees (BEAST) software. Values at branch points represent the estimated timing of divergence events in numbers of years before the present. Adapted from [45].