Press Briefing by White House COVID-19 Response Team and Public Health Officials

Walensky: “We do know the vast majority of viral transmission happens in those first five days, somewhere in the 85 to 90 percent range. So if a person can isolate for the first five days, they absolutely should.

Many are asking why do we not require a test at the end of the five days of isolation for those who are infected. We know that PCR testing would not be helpful in this setting, as people can remain PCR positive for up to 12 weeks after infection and long after they are transmissible and infectious.”