Earlier this week, the president’s doctors suggested they would work closely with military medical research facilities and other laboratories on “advanced diagnostic testing” to determine when the president was no longer contagious, but did not elaborate.

Dr. Anthony Fauci, the government’s top infectious disease expert, said two negative PCR lab tests 24 hours apart are a key factor in determining whether someone is still contagious.

“So, if the president goes 10 days without symptoms, and they do the tests that we were talking about, then you could make the assumption, based on good science, that he is not infected,” Fauci said Thursday on MSNBC.