BETHESDA, Md. – 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 once again showed his willingness to disregard basic precautions to contain the novel coronavirus 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 claimed 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,” he 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 come 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.

It was the second straight day of confusion and obfuscation from a White House already suffering from a credibility crisis. And it raised more doubts about whether the doctors treating the president were sharing accurate, timely information with the American public about the severity of his condition.

Pressed about conflicting information he and the White House released on Saturday, Navy Cmdr. Dr. Sean Conley acknowledged that he had tried to present a rosy description of the president’s condition.

“I was trying to reflect the upbeat attitude that the team, the president, that his course of illness has had. Didn’t want to give any information that might steer the course of illness in another direction,” Conley said. “And in doing so, you know, it came off that we were trying to hide something, which wasn’t necessarily true. The fact of the matter is that he’s doing really well.”

Medical experts said Conley’s revelations were hard to square with the doctor’s upbeat assessment and talk of a discharge.

“There’s a little bit of a disconnect,” said Dr. Steven Shapiro, chief medical and scientific officer at the University of Pittsburgh Medical Center.

At the same time, Trump’s drive-by greeting was reminiscent of the moment in 2016 when he emerged from Trump Tower in the midst of the Access Hollywood tape scandal to greet his supporters on the street below.

But this move potentially exposed several people in his security detail to COVID-19.

According to CDC guidelines, “In general, transport and movement of a patient with suspected or confirmed SARS-CoV-2 infection outside of their room should be limited to medically essential purposes.”

Some Secret Service agents have expressed concern about the lackadaisical attitude toward masks and social distancing inside the White House, but there isn’t much they can do, according to agents and officials who spoke to the AP. This close to the election, thousands of agents are engaged on protective duty so they can be subbed out quickly should someone test positive.

Concern over Trump’s impromptu drive capped a day when doctors’ revelations about his oxygen levels and steroid treatment suggested the president is enduring more than a mild case of COVID-19.

Blood oxygen saturation is a key health marker for COVID-19 patients. A normal reading is between 95 and 100. Conley said the president had a “high fever” and a blood oxygen level below 94% on Friday and during “another episode” on Saturday.

He was evasive about the timing of Trump’s oxygen drops. (“It was over the course of the day, yeah, yesterday morning,” he said) and asked whether Trump’s level had dropped below 90%, into concerning territory. (“We don’t have any recordings here on that.”) But he revealed that Trump was given a dose of the steroid dexamethasone in response.

At the time of the briefing, Trump’s blood oxygen level was 98% – within normal rage, Trump’s medical team said.

Signs of pneumonia or other lung damage could be detected in scans before a patient feels short of breath, but the president’s doctors declined to say what those scans have revealed.

“There’s some expected findings, but nothing of any major clinical concern,” said Conley, who declined to outline those “expected findings.”

Asked about Conley’s lack of transparency, White House aide Alyssa Farah suggested the doctors were speaking as much to the president as to the American public: “When you’re treating a patient, you want to project confidence, you want to lift their spirits and that was the intent.”

Biden, Trump’s Democratic challenger, has pulled his attack ads off the air during Trump’s hospitalization. On Sunday, he dispatched senior aides to deliver a largely friendly message.

“We are sincerely hoping that the president makes a very quick recovery, and we can see him back out on the campaign trail very soon,” Biden adviser Symone Sanders said on CNN’s “State of the Union.”

She added, “This is a glaring reminder that the virus is real.”

Biden was at home in Wilmington, Delaware, on Sunday with no plans for in-person campaigning or other public appearances. Having already tested negative, he is expected to release the results of a new coronavirus test later in the day. His campaign has pledged to disclose those results and all other future test results for the 77-year-old candidate.

Trump’s medical team indicated that his hospital stay could end soon.

“Our plan for today is to have him eat and drink, to be up out of bed as much as possible, to be mobile,” Dr. Brian Garibaldi said. “And if he continues to look and feel as well as he does today, our hope is that we can plan for a discharge as early as tomorrow to the White House where he can continue his treatment course.”

More than 209,000 Americans have been killed by the virus, by far the highest number of confirmed fatalities in the word. In all, nearly 7.4 million people have been infected in the United States, and few have access to the kind of around-the-clock attention and experimental treatments as Trump.

Trump’s treatment with the steroid dexamethasone is in addition to the single dose he was given Friday of an experimental drug from Regeneron Pharmaceuticals Inc. that supplies antibodies to help the immune system fight the virus. Trump on Friday also began a five-day course of remdesivir, a Gilead Sciences drug currently used for moderately and severely ill patients. The drugs work in different ways – the antibodies help the immune system rid the body of virus, and remdesivir curbs the virus’ ability to multiply.

Garibaldi, a specialist in pulmonary critical care, said the president was not showing any side effects of the drugs “that we can tell.”

The National Institutes of Health COVID-19 treatment guidelines recommend against using dexamethasone in patients who do not require oxygen. It has only been proven to help in more serious cases. Among the concerns with earlier use is that steroids tamp down certain immune cells, hindering the body’s own ability to fight off infection.

Trump is 74 years old and clinically obese, putting him at higher risk of serious complications.

First lady Melania Trump has remained at the White House as she recovers from her own bout with the virus.

Several White House officials this weekend expressed frustration with the way level of transparency and public disclosure since the president announced his diagnosis early Friday.

They were particularly upset by the whiplash between Conley’s rosy assessment Saturday and Meadows’ more concerned outlook. They privately acknowledge that the administration has little credibility on COVID-19 and that they have unnecessarily squandered what remains of it with the lack of clear, accurate updates on Trump’s condition.

Many in the White House are also shaken and scared – nervous that they have been exposed to the virus and confronting the reality that what seemed like a bubble of safety has become a COVID-19 hot spot. There has been no mass directive sent to staff on how they should respond.

Peoples reported from New York. Miller reported from Washington. Associated Press writers Lauran Neergaard and Jonathan Lemire in Washington, and Bill Barrow in Wilmington, Del., and Marilynn Marchione in Milwaukee contributed to this report.

President briefly leaves hospital to show supporters he’s fine