Trump’s health and COVID-19: Here’s what we know

President Donald Trump’s announcement that he and first lady Melania Trump tested positive for the coronavirus added a powerful and unpredictable factor to the presidential election.

Trump’s physician said that "both are well at this time and plan to remain at home within the White House during their convalescence." White House chief of staff Mark Meadows told reporters that Trump is experiencing "mild symptoms."

Later in the day, though, Trump was expected to leave for Walter Reed Medical Center on the advice of his doctors. The White House said he had mild symptoms but would work from Walter Reed as doctors monitored his condition.

The great majority of people who test positive for the coronavirus suffer no or minor effects. Based on what we know now, the odds for Trump weathering COVID-19 are in his favor.

But Trump has two risk factors — his age and his weight.

In June 2020, presidential physician Sean Conley told reporters that Trump weighed 244 pounds. At 6 feet 3 inches tall, the president had a body mass index of 30.5. A body mass index over 30 is considered obese. He is 74 years old.

Conley said in May that Trump is "in very good health." At the time, Trump talked up the benefits of using hydroxychloroquine to stave off the disease. We don’t know the extent to which Trump was taking it or if he continues to take it, but there is little sign the drug is effective.

Reports from Trump’s official White House physician show that he has wrestled with high cholesterol, but aggressive use of the drug rosuvastatin has brought his numbers down. His total cholesterol stood at 167 with an LDL — so-call "bad cholesterol" — below 100. Anything under 100 is considered optimal.

 In 2018, a coronary calcium CT scan showed that he had a count of 133. A count over 100 indicates plaque is present, which meets the definition of mild heart disease.

Trump made an unscheduled visit to Walter Reed Hospital in November 2019. He was there for a little over two hours. His press secretary said he was taking advantage of a free weekend to take care of tests that are part of his regular checkups. When questions came up about the trip, Trump described it as a routine physical.

The matter faded until this September when a book by New York Times reporter Michael Schmidt said he had learned that "word went out in the West Wing for the vice president to be on standby to take over the powers of the presidency temporarily if Trump had to undergo a procedure that would have required him to be anesthetized."

Pence said he didn’t recall being put on alert, and Schmidt said the episode remained a mystery.

Dr. David Hamer, professor in infectious disease at Boston University’s School of Public Health and School of Medicine, said that Trump’s age presents the biggest risk factor for him.

"Someone in his age group has an 8% to 12% chance of having severe illness," Hamer said.

That’s based on large studies out of Italy and China. In the China study, the risk of death for those 65 to 74 was half that of people 75 or older.

The Centers for Disease Control and Prevention lists a body mass index over 30 as increasing the "risk of severe illness from COVID-19." But most of the studies behind that focused on people with a body mass index of 35 or above. Trump is barely in the obese range.

RELATED: Donald Trump doesn’t meet the definition of morbidly obese

An American-based study found an increased risk for people with a body mass index in the 30 to 34.9 range, but the magnitude of the increased risk varied greatly in the data, from nearly none at all to a very large impact. In other words, it is difficult to pin down.

In general, men are more at risk than women. Globally, more men than women have died from COVID-19, but researchers don’t know exactly why.

Editor's note: This story was updated after it was first published to include Trump's scheduled departure for Walter Reed.