An attending physician at Walter Reed National Military Medical Center on Sunday swiped at President Trump for leaving his hospital room and waving to supporters gathered outside from his motorcade, saying it puts those in the vehicle at risk.

"That Presidential SUV is not only bulletproof, but hermetically sealed against chemical attack. The risk of COVID19 transmission inside is as high as it gets outside of medical procedures. The irresponsibility is astounding. My thoughts are with the Secret Service forced to play," tweeted James Phillips, who is also the chief of disaster medicine at the George Washington University Department of Emergency Medicine.

"Every single person in the vehicle during that completely unnecessary Presidential 'drive-by' just now has to be quarantined for 14 days. They might get sick. They may die. For political theater. Commanded by Trump to put their lives at risk for theater. This is insanity," he continued.

In photos and videos released by the White House, there is hardly any sign that Mr. Trump is sick. But at a news conference at the Walter Reed National Military Medical Center in Bethesda, Md., Mr. Trump’s doctors said his oxygen levels had dropped to a level that can indicate that a patient's lungs are compromised. The symptom is seen in many patients with severe Covid-19.

The president’s medical team also said that he had been prescribed dexamethasone on Saturday. The drug is a steroid used to head off an immune system overreaction that kills many Covid-19 patients.

The drug is reserved for those with severe illness, because it has not been shown to benefit those with milder forms of the disease and may even be risky.