January 21 — CDC Confirms First US Coronavirus Case--https://www.ajmc.com/view/a-timeline-of-covid19-developments-in-2020
FEBRUARY 3, 2020
US implements mandatory quarantines for first time in 50+ years over new coronavirus
https://www.advisory.com/daily-briefing/2020/02/03/coronavirus-update
Correction taken: 13 days is not technically immediate
Also, China began a kind of quarantining, at a macro level much earlier than I realized; but not apparently at homes and localized institutions. They kept two districts quarantined, the first population numbered at above 1 million, but only apparently that they couldn't leave those districts.
The thing is, today, the reader can't verify revision dates of articles, electronic. For example, a year or more ago I had pulled a replica of the US Bill of Rights to read the First Amendment discretely. The source was the American Historical Society. The source utterly corrupted the content of the first amendment. Months later when I attempted to expose it, I couldn't find it. Conspiracies do exist and they begin subtle and remain so until they bite you.