AURORA | When MeriLou Johnson first started working in AIDS research at the University of Colorado more than 20 years ago, people with the infectious disease had a dire prognosis.

Now, with the advancement of drugs to help combat the virus, people with AIDS are living longer, healthier lives.

“It’s a really different epidemic than it was when it started,” said Johnson, program director of the Colorado AIDS Education and Training Center at the University of Colorado Denver.

But only about 1 in 4 Americans with the AIDS virus have the infection under control with medications, federal health officials said Nov. 29.

Part of the reason is that about 20 percent of those infected with HIV don’t know it. People can have an infection for years without developing symptoms. In turn, those individuals are primarily responsible for the majority of new infections, Johnson said. “If we can catch people early in infection and get them on treatment, then the chance of them infecting additional people unknowingly drops dramatically. It’s a huge public health issue,” said Johnson, who is also an associate professor of medicine in the Division of Infectious Diseases at the University of Colorado.

She lauded the Nov. 29 announcement by the Centers for Disease Control of a $2.4 million campaign to encourage HIV testing. It’s the government’s first campaign aimed specifically at black gay and bisexual men, who account for nearly a quarter of all new HIV infections in the United States.

In its first study of the issue, the Centers for Disease Control and Prevention found only a small fraction of people are being successfully treated.

“The big picture is we could do a lot better than we’re doing today,” said Dr. Thomas Frieden, the CDC’s director.

Of the nearly 1.2 million people with HIV, only about 40 percent 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. The HIV virus can cause AIDS, an illness that destroys the body’s immune system and causes about 16,000 deaths annually.

Success rates were lowest in blacks and women than in others, the CDC also found. There are various reasons why more people aren’t doing better, health officials said. Some were still early in their treatment, when the virus hadn’t been beaten down to low levels yet. Some dropped routine care because of money or other obstacles. Some didn’t stick with it for other, more personal reasons. And, in a small percentage of cases, the medicine may not have worked.

In the United States, the number of new infections each year has held steady in recent years, at about 50,000.

The CDC analysis was based on several sets of data, including surveys and surveillance reports from 2010 and a study that looked specifically at the medical care of people with HIV.

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, health officials said.

Between 1982 — when Colorado health officials first started tracking data on the virus statewide — and December 2010, about 16,500 people were diagnosed with HIV in Colorado, Johnson said.

The rate of HIV in Colorado has steadily increased at about 3 percent per year, with about 430 cases of infection reported each year. About 89 percent of those infected are male.

Johnson said the University of Colorado offers comprehensive care for people living with HIV, care that covers not just the infection but also spans to include dermatological concerns and mental health programs. The university has also been engaged in clinical trials for several years, researching new treatments and ways to improve care, she said. The University of Colorado Hospital has also facilitated organ transplants for people with HIV.

“That used to be totally prohibited, but what that speaks to is how normalized and how effective treatment of HIV has gotten,” Johnson said.

But there are still not enough people being diagnosed, and there’s a worrisome gap between those who are diagnosed and those who get in — and stay in — treatment, some experts said.

“It’s not good enough to get them tested,” said Dr. Diane Havlir, who runs the AIDS program at San Francisco General Hospital.

San Francisco has been unusually aggressive about closing that gap. Patients are routinely tested for HIV at emergency rooms, and everyone who is diagnosed with HIV is offered treatment. Elsewhere, medical treatment can be delayed until their immune system dips to a certain level.

The Associated Press contributed to this report.

Reach reporter Sara Castellanos at 720-449-9036 or sara@aurorasentinel.com.