U.S. President Donald Trump left the Walter Reed National Military Medical Center on Sunday to greet supporters.

The short journey was intended to dismiss his illness and confirm his determination to push through with his election campaign, according to his political helpers. It was also a disregard of safety protocols, health and safety officials said. The virus has claimed the lives of more than 209,000 Americans.

The move has also puzzled medical experts and critics who thought the motorcade - in which he was seen inside a black Suburban SUV waving and saluting to his supporters -- was an unnecessary political stunt.

Moments before the motorcade, the president's medical team disclosed that his blood oxygen level fell unexpectedly twice in the past days and that he was administered with another kind of steroid. His physicians said his condition is getting better as he recovers from a COVID infection - and one of them said he could be discharged as early as Monday.

One of the attending doctors at Walter Reed was critical of Sunday's drive-by. Dr. James Phillips, an assistant emergency medicine professor at George Washington University, said that every single person in the SUV during that motorcade has to be placed in isolation for 14 days. "They might get sick. They may die," Al-Jazeera News quoted him as saying in a Twitter post.

But Trump said he has learned many things about the disease. In a video released on Twitter on the same day, while being treated for his sickness, he says his illness is "the real school," and that he understands it. The quick drive-by, he explained, was simply done to give his supporters "a little surprise," Bloomberg News reported.

Trump has played down the coronavirus pandemic and, before he tested positive from the disease, he rarely wore any face covering. The World Health Organization and scientists say face masks, proper washing of hands and physical distancing are important to preventing the spread of the virus.