Someone said :
Why do 60 health care workers need to self isolate. Can blood tests not be done or does it develop over two weeks?
The test takes time.
The latest most effective ones take a few hours but are not widely available.
The 2 weeks is the time it can take for Infected people to get sick.
And the test is not likely to be effective in case of low viral load: more sensitive tests take longer and are more expensive...
People are too used to Startrek style of médecine where a virus is isolated in an hour and a cure is found before the end of the episode, usually involving replacing every cell in the body via a novel genetic therapy miracle.