I think once their is some population immunity, that you start to put more effort into confirming people really are infectious. It's partially why I don't think the CDC rules about not requiring a test after the fifth day really matters in most places in the United States - 20+% of people in the general population are already infected in places like New York. Wearing a mask for 5 days after quarantining for 5 days, while not ideal - ensures that our medical and logistic and other critical systems keep working for the next 3-4 weeks.