[yokaze]

AFAIK, they are different tests:

* PCR tests to check if you are carrier of the virus right now. That's what you do with patients and personnel.

* Anti-body tests to gauge the number of people having been exposed to the virus in the past.

It takes a couple of days to develop anti-bodies so you don't want to use that one for the first use-case. And you can have anti-bodies without carrying the virus. (Well, it depends on the type of antibodies)

If you know the exposure in the general public, we would better know the real mortality, how far we are with herd-immunity, and if general quarantines do make sense, or it might be sensible to be more selective.