nextstrain.org, CC BY

Whilst I was laid up with COVID* I got to wondering about the number of folk the virus passed through during its journey from a bat in Wuhan to me in Yorkshire.

A quick Fermi estimate suggested something rather surprising: Assuming it takes 5 days, on average, from infection to transmission to the next person (which seems reasonable given viral load peaks around 5 days) and the virus crossed to humans at the beginning of November 2019. Then COVID…