(CBS/AP) Once a death sentence, AIDS can now be managed so effectively that people with the disease can live almost as long as those without it - but that's true only for those who get good medical care.
Unfortunately only one in four Americans with AIDS has the virus under control, according to a new CDC report.
"The big picture is we could do a lot better than we're doing today," said Dr. Thomas Frieden, the CDC's director.
Why is the treatment success rate so low? Partly because, of the 1.2 million Americans who have HIV - the infection that causes AIDS - 20 percent don't know they're infected. That's 240,000 people. People can have the infection for years without developing symptoms.
Another reason for the low success rate, only about 40 percent of people with HIV are getting HIV-fighting medications regularly. Worse, only 28 percent have gotten the virus to low levels in their blood. That translates to roughly 850,000 Americans who don't have the virus controlled, Frieden said.
Success rates were lowest in blacks and women, he said.
"The fact that nearly three quarters of Americans living with HIV still have the virus circulating in their bodies, damaging their brains and immune systems and putting their sexual partner at risk is something we think we can do a lot about," Frieden told Reuters.
The report - published Tuesday on the CDC's website - was based on surveys and surveillance reports from 2010 and a study that focused on medical care for people with HIV.
There are several reasons why more people aren't faring better, the CDC said. Some were still early in their treatment before medication took effect. Some dropped routine care because of money or other reasons. For a small percentage of cases, the treatment may not have worked.
The good news is that once HIV-infected people get plugged into medical care, the drugs bring the virus under control nearly 80 percent of the time. The bad news? Not enough people are being diagnosed, and the gap between those who are diagnosed and those who get in - and stay in - treatment is worrisome, according to AIDS experts.
"It's not good enough to get them tested," said Dr. Diane Havlir, chief of the HIV/AIDS program at San Francisco General Hospital.
San Francisco has been unusually aggressive in its techniques to buck this trend. Patients are routinely tested for HIV at emergency rooms, and everyone who is diagnosed with the infection is offered treatment. In other hospitals, treatment is sometimes delayed until the patient's immune system dips below a certain level.
Health officials elsewhere in the U.S. are trying unique approaches to get more people diagnosed. A Department of Motor Vehicles office in Washington D.C. offers people waiting for address changes and new licenses a $5 gift card if they get an HIV test, in an attempt to lower the city's high infection rate,reported.
On Tuesday, the CDC also announced a $2.4 million new campaign that encourages HIV testing among black gay and bisexual men, who account for nearly a quarter of all new HIV infections in the United States.
About 16,000 people die from the disease annually, and the number of new infections each year in the U.S. has held steady at about 50,000 in recent years.
WebMD has more on HIV/AIDS.