On the founder effect in COVID-19 outbreaks: how many infected travelers may have started them all?

How many incoming travelers ( at time 0, equivalent to the 'founders' in evolutionary genetics) infected with SARS-CoV-2 who visit or return to a region could have started the epidemic of that region? would be informative about the initiation and progression of epidemics. To obtain , we analyze the genetic divergence among viral populations of different regions. By applying the 'individual-output' model of genetic drift to the SARS-CoV-2 diversities, we obtain < 10, which could have been achieved by one infected traveler in a long-distance flight.