Von Miller has tested positive for COVID-19.

"It's true," Miller told 9NEWS by phone. "I've just been here in the crib, and I started to get a little cough. You know, I have asthma, and I started getting a little cough a couple days ago. My girlfriend ... she told me when I was asleep, she said my cough, it didn't sound normal."

Miller said a nebulizer didn't help, and his assistant persuaded him to go to the doctor to get tested on Tuesday.

"It's crazy,'' Miller told 9NEWS. "I have to be quarantined here at the house. There's not really any medicine or anything like that. Dr. [Steve] Geraghty told me if my breathing changed ... honestly, I'm still new to this. This is like an hour [since learning I tested positive]. I'm not sure what's going on, but I tell you what, I'm in good spirits. I'm still Von. I'm not feeling sick or hurting or anything like that."