Kim Painter

Special for USA TODAY

Anti-HIV drugs work to extend lives and slow the spread of the AIDS virus, but fewer than half of infected gay and bisexual men in the United States took those medications in recent years, a new report says.

Treatment was especially scant among young men and black men, says the report from the federal Centers for Disease Control and Prevention, published Thursday in Morbidity and Mortality Weekly Report.

The report is the latest evidence that "one of the most powerful tools for protecting people's health and preventing new HIV infections is reaching only a fraction of the gay men who need it," says David Purcell, deputy director for behavioral and social science in the CDC's HIV prevention division.

The report shows that 77% of gay and bisexual men newly diagnosed in 2010 got some initial care, as evidenced by lab reports from 19 areas around the country.

But researchers found just 51% of all infected gay and bisexual men in those areas got continuing care. An additional nationwide analysis found 49.5% were prescribed drugs that can suppress the virus, preventing it from destroying the immune system. Those medications can allow patients to live for decades and greatly reduce their risk of spreading the virus.

Drug treatment rates were just 30% in infected men under age 25 and rose with age, reaching 68% in men 55 and older. Rates also varied by race; black men got treatment less often than Hispanic and white men.

Federal health officials started recommending treatment for everyone with the virus, including those at the earliest stage of infection, in 2012, after the data were collected. But the treatment gaps found in the report most likely persist, Purcell says.

Men may stay away from treatment out of denial, because they don't understand the need, don't have insurance or for many other reasons, including perceived stigma, he says.

"People may not want to go to a clinic that is called 'the HIV clinic'," he says. Some may perceive health care providers in their communities as homophobic, he says. Young men may not know how to manage health care basics, such as making appointments.

The age differences in care also may reflect differences in how younger and older men perceive the HIV threat, says Noël Gordon, a project manager at the Human Rights Campaign, a gay rights advocacy group.

"Older gay and bisexual men lived through the crux of the crisis and have lost friends and partners," he says. Younger men are less likely to know others with HIV experiences or to talk about HIV among friends, he says.

CDC says nearly 600,000 of the 1.1 million people living with HIV in the United States are men who have sex with men, and two-thirds of new infections still occur in that group. Infection rates among gay and bisexual men, especially young men, have been rising in recent years, despite targeted prevention efforts.

About one-third of infected gay and bisexual men don't know they are infected, CDC says.

In a separate survey released Thursday, about one-third of gay and bisexual men said they had never been tested. More than half said a doctor had never suggested it. The nationally representative survey of 431 men, from the Kaiser Family Foundation, also found that nearly half had never even discussed their sexual orientation with a doctor.