They are almost certain that the virus was here before the 1st confirmed case on Jan 21 but it is not likely that it had been here too long and even less likely that it had spread much.

I was listening to an epidemiologist who said that, based on the info they’ve gained from sequencing the virus, it made the jump to humans around the 1st of December.

Based on a bunch of stuff I really don’t understand they said that it may have gotten here a couple of weeks earlier but that it wouldn’t have had time to spread to a significant percentage of the population (like the 20% you mentioned).

The general belief is that, as testing ramps up, we’ll see significantly higher numbers than what would be expected if the 1st case really was on Jan 21, but not to a degree that would indicate arrival much earlier than the 1st week in January.