ATLANTA – Twenty-five years after the first AIDS cases jolted the world, scientists think they soon may have a pill that people could take to keep from getting the virus that causes the global killer.

Two drugs already used to treat HIV infection have shown such promise at preventing it in monkeys that officials last week said they would expand early tests in healthy high-risk men and women around the world.

“This is the first thing I’ve seen at this point that I think really could have a prevention impact,” said Thomas Folks, a federal scientist since the earliest days of AIDS. “If it works, it could be distributed quickly and could blunt the epidemic.”

Condoms and counseling alone have not been enough – HIV spreads to 10 people every minute, 5 million every year.

If larger tests show the drugs work, they could be given to people at highest risk for HIV – from gay men in American cities to women in Africa who catch the virus from their partners.

Matthew Bell, a 32-year-old hotel manager in San Francisco, volunteered for a safety study of one of the drugs.

“As much as I want to make the right choices all of the time, that’s not the reality of it,” he said of practicing safe sex. “If I thought there was a fallback parachute, a preventative, I would definitely want to add that.”

Some fear that this could make things worse.

“I’ve had people make comments to me, ‘Aren’t you just making the world safer for unsafe sex?”‘ said Dr. Lynn Paxton, team leader for the project at the Centers for Disease Control and Prevention.

The drugs would only be given to people along with counseling, condoms and regular testing to make sure they haven’t become infected. Health officials also think the strategy has potential for more people than just gay men, although they don’t intend to give it “to housewives in Peoria,” as Paxton put it.

Some uninfected gay men are already getting the drugs from friends with AIDS or doctors willing to prescribe them to patients who admit to not using condoms. This kind of use could lead to drug resistance and is one reason officials are rushing to expand studies.

“We need information about whether this approach is safe and effective” before recommending it, said Dr. Susan Buchbinder, who leads one study in San Francisco.

The drugs are tenofovir (Viread) and emtricitabine, or FTC (Emtriva), sold in combination as Truvada by Gilead Sciences Inc., a California company best known for inventing Tamiflu, a drug showing promise against bird flu.

Unlike vaccines, which work through the immune system – the very thing HIV destroys – AIDS drugs simply keep the virus from reproducing. They already are used to prevent infection in health care workers accidentally exposed to HIV, and in babies whose mothers receive them.

Taking them daily or weekly before exposure to the virus – the time frame isn’t known yet – may keep it from taking hold, just as taking malaria drugs in advance can prevent that disease when someone is bitten by an infected mosquito.