The star will announce that he is HIV-positive on the Today show Tuesday
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Though Charlie Sheen will soon sit down for a Today show interview to discuss being HIV-positive, the star is telling people his health is on the upswing, a source with knowledge of the situation tells PEOPLE.

“He is saying there is virtually no trace of HIV in his blood. He’s taking antiretrovirals and is sticking to the regime, he says,” the source tells PEOPLE. “He is telling people the virus is now undetectable.”

Sheen, 50, flew from Los Angeles to New York Monday ahead of his interview with Today‘s Matt Lauer.

“He’s still HIV-positive. But he isn’t about to slow down,” the source says.

Earlier Monday, a source told PEOPLE that Sheen’s ex Denise Richards had known about the actor’s diagnosis for years.

“He was infected after they divorced, and they haven’t been intimate since,” said the source. “Neither she nor their daughters [Sam, 11, and Lola, 9] are HIV-positive.”

RELATED VIDEO: Denise Richards Knew Charlie Sheen Was HIV-Positive: Source

Sheen has long struggled with substance abuse and has admitted to soliciting prostitutes in the past. But Sheen’s former girlfriend Natalie Kenly told PEOPLE Monday that she does not believe he’d be recklessly promiscuous.

“He has regard for human beings and cares about people. I do not see him knowingly putting women at risk,” she told PEOPLE.

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