“The first known death in the U.S. was on Feb. 29.”
Actually that is the first acknowledged death date. There were people dying in the US from pneumonia, with a rapid and severe onset in November, most were written off as “the flu” did it.
That was my point. We do not what we know until we know it, and can not act on a problem while unaware of it. We did not know Corona virus was in the U.S. until late February. Anything we found out about its presence before February came later.