Von Miller, the second NFL player to disclose that he is infected with the coronavirus, said he was shocked when he tested positive.
The superstar Denver Broncos linebacker appeared Friday on the "TODAY" show from his home in Colorado wearing a gray hoodie and eyeglasses.
"It all started with just a simple cough and it got worse," Miller, 31, said.
Miller, who won the Most Valuable Player Award in Super Bowl 50, said he has asthma and his girlfriend had told him he wasn't sounding normal.
He said he tried a nebulizer, "but it really didn’t work like it should."
"And my assistant said, 'Why don’t you just get tested?'" Miller said.
He learned two days later of his diagnosis, which was first reported Thursday by NFL Network. A day earlier, Brian Allen, a center for the Los Angeles Rams, became the first active NFL player to reveal that he tested positive for the coronavirus.
Miller said Friday that when his doctor informed him of his positive result, "I was shocked."
He said he has been taking the pandemic seriously "since day one."
He was training in San Francisco when the city in mid-March issued a stay-at-home order. Right after that, he went to Denver where he lives and stayed there, Miller said.
In the four weeks he has been in Denver, Miller said he has left his house only four times and has had some people come to the house, such as a plumber and maids.
Asked about the possibility of playing to an empty stadium when the NFL season starts in the fall, which the league has been contemplating, Miller said: "Whatever's safe ... Whatever we have to do to get things back to normal, that's what we have to do."
"We shouldn't move too fast," Miller said.
Miller was the second overall pick in the 2011 draft. He has been selected to the Pro Bowl eight out of his nine years in the league.
In a statement Thursday, the Broncos said Miller is the first person in their organization to have tested positive for the virus.
Miller "elected to share his diagnosis publicly to emphasize that anyone can be afflicted with coronavirus," the statement said.