Actor Charlie Sheen shocked many of his fans when he announced on NBC's TODAY Show last week that he was infected with HIV.
Perhaps equally shocking for many was that he said he continued to have sex — and said he was confident he hadn't infected anyone else.
That's in part because of a once-a-day pill called pre-exposure prophylaxis or PrEP. It's been on the market since 2012 and has been recommended by the Centers for Disease Control and Prevention since 2014. Yet a third of U.S. doctors don't even know about it, and hundreds of thousands of people at high risk don't, according to a new survey by the CDC.
"PrEP isn't reaching many people who could benefit from it, and many providers remain unaware of its promise," said CDC Director Dr. Tom Frieden. "With about 40,000 HIV infections newly diagnosed each year in the U.S., we need to use all available prevention strategies."
Sheen's doctor, Dr. Robert Huizenga, is one of the two-thirds of doctors who did know about it, and he prescribed PrEP to several of Sheen's sexual partners.
"In numerous situations he would inform his partner and then he would often have the partner see me and we would have an incredibly frank discussion about their exact risks based on their known information and their options," Huizenga told NBC News.
Sheen's former girlfriend, nurse Amanda Bruce, was one of those partners. She took PrEP, which has been shown to lower the risk of infection by more than 90 percent.
"I did not know about a prophylactic medication that you could take as an HIV-negative person," Bruce told NBC News. "It's pretty cool."
The CDC released a survey Tuesday that showed 25 percent of sexually active gay and bisexual adult men - or more than 490,000 men — could benefit from PrEP. They found that more than 18 percent of adults who inject drugs should be taking it to protect themselves.
The pill's an HIV drug called Truvada, and because of the way it works, it can prevent infection as well as treat it.
"PrEP has the potential to dramatically reduce new HIV infections in the nation," added Dr. Jonathan Mermin, who heads CDC's HIV division. While condoms work best to prevent HIV infection, as well as other sexually transmitted diseases such as syphilis, people often don't use them. And condoms cannot help injecting drug users who don't have access to one-time-use needles.
Most Americans don't need PrEP. Only about a half of 1 percent of sexually active adults have a high risk of catching HIV. But that adds up to a lot of people — 1.2 million Americans at "substantial risk," CDC estimates.
Those at highest risk are men who have sex with men — bisexual and gay men. "In 2014, males accounted for 81 percent of all diagnoses of HIV infection among adults and adolescents," CDC said.
The next highest risk group are uninfected men or women in a relationship with someone who's HIV positive — like Bruce.
She says she was careful to use protection when she first started dating Sheen.
"That option of being unprotected was not even an option for me," Bruce said. "Once we became a couple, I decided not to use them any longer. That became another discussion."
Sheen took Bruce to see Huizenga.
"We have a moderate amount of HIV patients in my practice," Huizenga said. "One of the doctors in my group practice is an HIV expert."
So the partners knew about PrEP, as well as about the option that Sheen has to keep his HIV well-controlled using a cocktail of drugs.
Huizenga says the drug cocktail keeps Sheen's HIV levels undetectable. That doesn't mean the virus is gone, but it means it's circulating at such low levels that only specialized tests can detect it.
That in itself can protect his sexual partners from infection. PrEP adds another layer of protection.
Bruce said she knew that HIV cocktails could keep patients healthy and protect their partners from infection. She didn't know there was a drug option for her, too, even though she has worked as a nurse and is more up-to-date on medical options than most Americans are. She'd like to help get the word out to other people who might be at risk.
"If you happen to fall in love with someone, as I did, who happened to be HIV positive, you can be intimate. You can have children. You can have a normal life," she said.
Bruce didn't suffer any side-effects from the drug, although it can cause stomach upset.
Huizenga says all of his patients have tolerated the drug well. There is one barrier. "It's extremely expensive," Huizenga said. "If your insurance doesn't pay for it, you will get stuck with a very large bill."
That worries CDC, also. CDC estimates Truvada can cost $10,000 a year, although Medicaid pays for it and many private insurers do, too.
New York state's department of health says a fairly simple effort helped to get the word out. The program included a kit sent to primary care doctors as well as an organized community outreach program.
They quadrupled the number of Medicaid patients filling prescriptions for PrEP, from 303 in 2014 to 1,330 a year later.