[2006alum]

It is interesting that the prevalence stayed so low early in the year, then shot up so quickly in March. If that person in January had spread it widely, things would have been worse. It’s also possible the early cases self quarantined better, or weren’t social people (I wonder of they’ll provide more details on the two deaths).

That's what exponential growth looks like.  The number of cases creep up slowly, almost indistinguishably from background, and then will shoot up seemingly coming out from nowhere.

BC

Exactly. I was going to say - given how quickly we saw a large number of cases in CA in early March, there had to be a few cases as early as January, because the virus's standard R0 without intervention is 2-3, which means that one person who is infected on Jan. 1 will have inadvertently caused, on average, 2-3 more infections by Jan. 8, 4-9 infections by Jan. 15, 8-27 infections by Jan. 22, 16-81 infections by Jan. 29, and 32-243 infections by Feb. 6. If up to 243 people could have been infected from a single primary carrier who entered the community Jan. 1, it would be entirely predictable to see the first death by Feb. 6 with an IFR of 0.5-1.0% and over 200 people infected during that time period.

[2006alum]

It is interesting that the prevalence stayed so low early in the year, then shot up so quickly in March. If that person in January had spread it widely, things would have been worse. It’s also possible the early cases self quarantined better, or weren’t social people (I wonder of they’ll provide more details on the two deaths).

That's what exponential growth looks like.  The number of cases creep up slowly, almost indistinguishably from background, and then will shoot up seemingly coming out from nowhere.

BC

Exactly. I was going to say - given how quickly we saw a large number of cases in CA in early March, there had to be a few cases as early as January, because the virus's standard R0 without intervention is 2-3, which means that one person who is infected on Jan. 1 will have inadvertently caused, on average, 2-3 more infections by Jan. 8, 4-9 infections by Jan. 15, 8-27 infections by Jan. 22, 16-81 infections by Jan. 29, and 32-243 infections by Feb. 6. If up to 243 people could have been infected from a single primary carrier who entered the community Jan. 1, it would be entirely predictable to see the first death by Feb. 6 with an IFR of 0.5-1.0% and over 200 people infected during that time period.