No sooner had it become known that President Trump had tested positive for the coronavirus than controversy arose over the amount and detail and truthfulness of the information about his condition that was coming from the White House.

The timeline of Trump's diagnosis and treatment over the past few days continues to evolve. His medical team's briefings from Walter Reed National Military Medical Center have at times resulted in more confusion than clarity.

In the latest example, White House physician Sean Conley's Sunday press conference — like his Saturday one — seemed to raise more questions than it answered.

He said the president had received supplemental oxygen, after declining to confirm that on Saturday, and announced that Trump had started taking a steroid after a second drop in his oxygen levels. Conley explained some of his Saturday statements as "trying to reflect the upbeat attitude" of the doctors and Trump.

In an additional display of optimism, Trump even left the medical center to drive by and wave to supporters gathered outside on Sunday. In a rare move, the White House did not inform reporters that the president would be taking the excursion.

None of opaqueness should come as surprise, though. Few occasions of historical importance have been so shrouded in secrecy — and even outright deception — as the health emergencies of world leaders. The U.S. may have been more transparent about these events than most countries, but, even here, the truth has only come to light over time.

"This is one precedent this president is following," says Barbara Perry, director of Presidential Studies at the University of Virginia's Miller Center.

Perry says the American public has a right to know the health of their presidents, especially now, given that voters are also just weeks away from deciding at the ballot box who is most fit to inhabit the Oval Office.

"They used to say when the president gets a cold, the stock market drops," Perry says. "It really has an impact on people's lives, whether it's the economy, or in this instance, it would help us to know, is he now even capable of governing?"

Here are a few of the more egregious cases of obfuscation in the past, when the health of the president was in question while he was in office.