I’m not sure.
I would think testing can detect it once you are contagious even if asymptomatic.
The question is how long after being exposed do you become contagious?
If we knew the answer, that could shorten the quarantine periods.
Some anecdotal reports now say almost immediately, certainly within 24 hours. Chinese reports now indicate once the virus is airborne it stays for ? No reports yet how far they think it can travel...
Infected person does not have to be present. Chinese are busy blasting their surfaces and air over cities and streets with prob disinfectant