(CNN)Actor Charlie Sheen told NBC's "Today" show Tuesday that he was diagnosed as HIV-positive about four years ago, and that a few people who knew it demanded money from him to keep the secret."I'm here to admit that I am in fact HIV-positive," Sheen told NBC's Matt Lauer. "And I have to put a stop to this onslaught, this barrage of attacks and of sub-truths and very harmful and mercurial stories that are about the [alleged] threatening the health of so many others, which couldn't be farther from the truth."
Sheen, 50, said he is not sure how he contracted the virus. Since his diagnosis, he said, he has informed every sexual partner of his condition. He called it "impossible" that he had transferred the virus to others.He said the diagnosis came after he suffered a series of cluster headaches and night sweats."After a battery of tests ... they walked in the room and said, 'Boom, here's what's going on,'" Sheen said."It's a hard three letters to absorb," he said. "It's a turning point in one's life."He said he revealed the diagnosis to people he thought he trusted, but some of them demanded money to keep the information to themselves. He paid those people "in the millions," he said. Later in the show, Lauer said that Sheen told him it was more than $10 million."We're talking about shakedowns," Sheen said. "I've paid those people."One of those people, he said, was a prostitute who entered his bathroom, took a cellphone picture of his medication and threatened to sell the image.Asked if he would continue to pay the people he'd been paying, he said: "Not after today, I'm not."'Charlie does not have AIDS'Sheen was joined on the show by his doctor, Robert Huizenga, an assistant professor of clinical medicine at UCLA ,and was asked directly if he had AIDS."Charlie does not have AIDS," Huizenga said. "AIDS is a condition where the HIV virus markedly suppresses the immune system and you are susceptible to rare, difficult cancers and infections. Charlie has none of those. He is healthy; he does not have AIDS."HIV, or human immunodeficiency virus, attacks the immune system by destroying white blood cells, which are vital to fighting infection. Once enough of these cells have been destroyed and the person has another "opportunistic" infection like pneumonia or tuberculosis, the diagnosis moves to the final stage of the infection, called AIDS.There are two main ways HIV is spread in the United States -- by sex and by sharing needles, syringes or any of the equipment used to prepare and inject drugs. Anal sex carries the highest risk, followed by vaginal sex and having multiple partners.In the "Today" interview, Sheen denied any possibility that he got the disease via drug use. "No needles," Sheen said. He also said he was no longer on drugs, but did continue to drink and seek the company of prostitutes.In the past, Sheen has admitted to frequent visits to prostitutes at various times in his life. In July 1995, he testified in the tax evasion trial of "Hollywood madam" Heidi Fleiss that he had spent $53,000 in one 15-month period on "sexual services."