[lamontcg]

Nowhere in the US has really had harsh lockdown measures.

SF also has density issues that will drive up the r0 of the virus. While the widely quoted r0 of the virus is around 3.0, the r0 in NYC at the start of the outbreak was estimated to be 5.0

(You could argue about if that was really the r(t) and not r0, but I'm not considering time-dependence or the reaction to the virus, but the actual starting reproduction number in NYC before there was any human reaction to the virus -- that isn't a constant value but depends on the local conditions).

Austin has an overall 3,000 people per square mile density, SF has an overall 18,000 people per square mile (and some areas are even more dense than that).

[lancewiggs]

Density is not an issue - just stay inside. Overcrowding per household is a big issue.