The president had already tested positive Thursday when he appeared on Fox News.
President Donald Trump's condition is continuing to improve as he fights a coronavirus infection, doctors say, and he may be able to leave Walter Reed Medical Center as early as Monday -- even as details emerge that the president allegedly initially tested positive for COVID-19 earlier than he acknowledged.
Doctors also reported that Trump, over the course of exhibiting coronavirus symptoms, had earlier experienced two episodes of "transient drops" in his oxygen saturation.
Yet the president was feeling well enough Sunday evening to briefly leave Walter Reed for a surprise drive-by, waving to supporters outside the hospital.
Meanwhile, numerous questions remain about how many people at the highest levels of government had been exposed to the virus after a week of events involving the president where social distancing and mask-wearing were lax in the White House and elsewhere.
Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases and a member of the White House coronavirus task force has not been consulted on the treatment of President Trump, according to a source familiar with the president's treatment.
-ABC News' Chief White House Correspondent Jonathan Karl
ABC News has confirmed two White House residence staff members tested positive for the coronavirus a few weeks ago, according to sources familiar with the matter.
The sources told ABC News the employees did not come into direct contact with President Trump or first lady Melania Trump.
White House spokesperson Judd Deere would not comment on the individuals but told ABC News the White House "does take any positive case seriously and has extensive plans and procedures in place to prevent further spread," he said. "A full and complete contact trace consistent with CDC guidelines is included in that and appropriate notifications and recommendations are made. "
The news was first reported by the New York Times.
-ABC News' John Santucci
The medical team refused on Saturday to confirm that President Trump was given supplemental oxygen as part of his treatment for the coronavirus, but on Sunday Dr. Sean Conley said the president had been in fact given supplemental oxygen at least once.
Sources close to Trump told ABC News the president was having trouble breathing and received supplemental oxygen on Friday at the White House after his oxygen levels dropped. This in part prompted the president to be transferred to Walter Reed Hospital late Friday afternoon.
When asked why that information was not disclosed until Sunday, Conley said he was "trying to reflect the -- the upbeat attitude that the team, the president, that this course of illness has had."
"I didn't want to give any information that might steer the course of illness in another direction. And in doing so, you know, it came off that we were trying to hide something which wasn't necessarily true."
Conley was asked if Trump had been given a second round of supplmental oxygen on Saturday and he said he'd "have to check with the nursing staff" but if additional oxygen was administered, it would have been "very, very limited."
Dr. Sean Conley and the medical team were asked about videos that showed President Trump not wearing a mask while updating the public on his current condition.
Conley told reporters on Sunday that the president "wears a mask anytime he's around us" and that all hospital officials are wearing their N95 masks and full personal protective equipment.
