A quarter of gay urban men have unprotected sex with casual partners, despite millions of dollars spent on HIV/ AIDS prevention strategies, according to new research published Thursday.

Researchers at the Centers for Disease Control and Prevention surveyed residents of 21 cities in 2008 who were high risk for contracting the human immunodeficiency virus: men who have sex with men, injection-drug users and increased-risk heterosexual adults.

The group, led by Teresa Finlayson, estimated that 1.1 million U.S. residents live with HIV, a number consistent with other reports.

The epidemiologists also found that despite the possibility of contracting HIV, first identified in five gay men in 1981, over half of the gay men surveyed (54 percent) had had unprotected anal sex in 2008.

Thirty seven percent reported unprotected anal sex with a single male partner, which significantly lowers risk of HIV transmission when both men are HIV negative and monogamous.

However, 25 percent of gay men had unprotected anal sex with someone with no feelings of commitment, didn't know well or exchanged for money or drugs.

It's really sad when you see these numbers, unfortunately it's not surprising from people who work in the HIV/ AIDS community, said Vignetta Charles, senior vice president for AIDS United, a group that advocated HIV prevention. This is just an indication of resource allocation disparities that we've seen for years.

For example, young black men who have sex with men, one of the highest risk groups, have disparate information on prevention and social barriers to seeking help, Charles said.

Young urbanites may have a level of disinhibition as HIV becomes considered a chronic disease or gay men perceive their activities as low risk.

Another reason we're seeing stark behavioral data: all prevention is not the same, Charles said. HIV prevention strategies for young black gay men differs strategies for middle-aged white women, for example.

Of the survey participants, which included injection drug users and high-risk heterosexual people, 90 percent had been tested for HIV during their lifetime, 62 percent had been tested during the past 12 months and 18 percent had participated in an individual- or group-level HIV behavioral intervention.

The stigma of sex, compounded by gay sex and anal sex, has produced a barrier for conversations about HIV prevention.

What stigma does is make it difficult for people to talk about protection, prevention and disclosure, John Guidry, director of community health and research for Gay Men's Health Crisis said. That would be one of the biggest things driving this.

The organization in 2010 rolled out its I Love My Boo campaign throughout New York City, which showed posters of men of color being affectionate.

It provoked a real conversation in New York, Guidry said. However, he added, Reducing stigma is nothing you can do with a silver bullet.

In 2010, the Obama administration unveiled a 5-year $30 million strategy to lower the rate of annual infections by 25 percent, a rate that has stubbornly remained stable for the past decade.

Now, I know that this strategy comes at a difficult time for Americans living with HIV/AIDS, because we've got cash-strapped states who are being forced to cut back on essentials, including assistance for AIDS drugs, U.S. President Barack Obama said during the unveiling ceremony. I know the need is great.

The Gay Men's Health Crisis's future efforts to reduce stigma includes a mix of resiliency-based campaigns that empowers people at risk instead of keeping them quiet.

That work includes marriage social media, community health fairs, presenting both male and female condoms in a way that isn't heavy handed. Further, the group is also supportive of pre-exposure prophylaxis; anti-retroviral drugs that evidence suggests can stave off HIV before it infects an exposed person.

We have to present the whole array because some things will work for some people better, Guidry said.