The average person is PCR+ for ~30+ days but infectious for ~7.
Most people are asymptomatic. So, infrequent PCR based surveillance will detect + people but ~75% will no longer be transmitting virus
1/...
2/
If performing random testing on asymptomatics, most who are Found to be positive will be discovered only after the first week or so of infection...
3/
So we need to not test randomly for people, we need test frequenty...
4/
5/
If sick, get a PCR test and discuss with your doctor
If not symptomatic, etc, a one time test provides very little information.