Two days after being hospitalized with COVID-19, President Donald Trump declared, “I get it,” in a message to the nation Sunday before briefly leaving the hospital to salute supporters from his motorcade, a move that again showed his willingness to disregard basic precautions to contain the virus that has killed more than 209,000 Americans.

Hours earlier, Trump’s medical team reported that his blood oxygen level dropped suddenly twice in recent days and that they gave him a steroid typically only recommended for the very sick. The doctors also said his health is improving and that he could be discharged as early as Monday.

“It’s been a very interesting journey. I learned a lot about COVID,” Trump said, standing in his hospital room in a video posted on social media. “I learned it by really going to school.”

He added, “I get it, and I understand it.”

Before the video was posted, the infected president cruised by supporters in his sealed SUV, windows rolled up, driven by Secret Service agents in protective gear who were potentially exposed to the disease that has swept through the White House in recent days.

“This is insanity,” tweeted Dr. James P. Phillips, an attending physician at Walter Reed National Military Medical Center, where Trump has been hospitalized since Friday evening.

“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,” the doctor wrote. “For political theater. Commanded by Trump to put their lives at risk for theater.”

Meanwhile, former Vice President Joe Biden’s campaign said the Democratic presidential nominee again tested negative for coronavirus Sunday. The results came five days after Biden spent more than 90 minutes on the debate stage with Trump. Biden had two negative tests on Friday, as well.

Trump’s doctors earlier in the day sidestepped questions about exactly when Trump’s blood oxygen dropped — an episode they neglected to mention in multiple statements the day before — or whether lung scans showed any damage.