With U.S. President Donald Trump's recent COVID-19 diagnosis, some are questioning how transparent the White House is being about his health.

The White House initially said the president was experiencing "mild symptoms" on Friday. In a press conference after being admitted to Walter Reed Medical Center, his doctors gave a positive prognosis but then Chief of Staff Mark Meadows later said the president experienced a "very concerning" period on Friday. Meadows said the next 48 hours would be critical in his care.

Secrecy surrounding a U.S. president's health is nothing new. 
Here are other cases of presidents hiding details surrounding their health:

Woodrow Wilson: The 28th president of the U.S. suffered a stroke in 1919 that nearly killed him and paralyzed his entire left side. The full details of his condition, however, were not disclosed to the public. 

Wilson completed the last 17 months of his term as a "recluse," wrote historian Thomas J. Knock.

"Wilson was but a frail husk of his former self, a tragic recluse in the White House shielded by his wife and doctor."

The White House also kept secret the health problems of Wilson's successor, Warren G. Harding, including the heart disease that contributed to his fatal heart attack in 1923.

Franklin D. Roosevelt: The 32nd U.S. president had overcome polio, but used a wheelchair. He established informal rules with the press, with coverage that did not focus on his physical disabilities. Few photos of him in his wheelchair were ever published.

John F. Kennedy: The 35th U.S. president suffered from hypothyroidism, fevers, stomach, colon and adrenal gland issues. Kennedy was also diagnosed with Addisons disease, an endocrine disorder.

Despite presenting an image of youth and "vigor" during his campaign and while in office, biographer Michael Kazin said he had a "variety of ailments that frequently confined him to bed and plagued him throughout his life."

Ronald Reagan: Just two months after taking office in 1981, the 40th U.S. president was shot at close range in Washington, D.C.

According to Del Quintin Wilber, a Washington Post reporter who wrote a book about that day called Rawhide Down, Reagan lost almost half his blood volume and came within seconds of dying.

But the information released to the public was different. White House spokesmen left out details of Reagan's serious brush with death and instead focused on upbeat bedside anecdotes, like Reagan joking and bantering with doctors.

During his second term, signs of deteriorating mental acuity started to appear but went mostly unreported. 
Five years after leaving office, Reagan was diagnosed with Alzheimer's Disease.

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