Last week, actor Charlie Sheen revealed to that he was HIV-positive. He said he was diagnosed about four years ago, and is coming out now mainly because he was being blackmailed by various people who knew about it and were demanding money to keep silent. Sheen said he paid those people more that $10 million to keep quiet.

As for how Sheen contracted HIV, he said he is not sure how it happened. He also said that since being diagnosed, he has informed every sexual partner he’s had and that he was sure, i that he had not given it to them, going so far as to say it would be "impossible."

HIV can be spread several ways including through intercourse and sharing needles. Although Sheen has a history of drug use, he denied any possibility of contracting the virus through sharing needles. He did admit to having frequent visits with prostitutes in his life.

Many people wonder how Sheen appears to be as healthy as he does. Other than his frequent public mishaps with drug and alcohol use, he certainly does not appear nor claim to feel “sick”. Before Sheen was diagnosed, he does recall experiencing frequent headaches and night sweats. What is the explanation for this?

It is true Sheen is HIV-positive, however, the virus has not transformed into AIDS, or acquired immune deficiency syndrome. When Sheen publicly revealed his diagnosis, he was accompanied by his doctor, Robert Huizenga, who is an assistant professor of clinical medicine at UCLA.

"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 stands for human immunodeficiency virus. The virus attacks the immune system by destroying white blood cells, which are essential for the body to fight infection. Once enough white blood cells have been destroyed and the immune system has become detrimentally weak, the person often develops additional "opportunistic" infections. It is at this stage that the HIV is able to develop into full blown AIDS.

Once diagnosed, Sheen was put on a treatment plan consisting of strong antiviral drugs to suppress the virus. When people like Sheen, and more notably Magic Johnson, are treated with an antiviral "cocktail," the risk of transferring the virus becomes significantly lower. And the key to keeping the virus from developing into AIDS is by staying on the medication every day. If the virus cannot replicate, it cannot develop resistance, and then cannot develop into AIDS. This is how people like Johnson have been able to live for as long as they have and at the same time, live a relatively healthy life.

Most people think of HIV as a death sentence. However, with the advancements in medicine, it no longer is. If a person is  diagnosed with HIV, and it has not turned into AIDS, it is very possible to live a relatively normal life as long as they get adequate care and stay on their medications.

Dr. Samadi is a board-certified urologic oncologist trained in open and traditional and laparoscopic surgery and is an expert in robotic prostate surgery. He is chairman of urology, chief of robotic surgery at Lenox Hill Hospital and professor of urology at Hofstra North Shore-LIJ School of Medicine. He is a medical correspondent for the Fox News Channel's Medical A-Team and the chief medical correspondent for am970 in New York City. Learn more at roboticoncology.com. Visit Dr. Samadi's blog at SamadiMD.com. Follow Dr. Samadi on Twitter and Facebook.