This is a big topic. If we tested a nurse today and that was negative and then worked 2 more shifts possibly exposed would you test them again in a week?........ the working and testing could go on and on. That's why I think its good for all healthcare workers to wear masks at all times. Maybe get a baseline test, where a mask at all times, and then test only if there are symptoms. However if you are in an area without enough PPE maybe you won't be able to mask at all times.