CHICAGO - More than half of young people in the United States infected with HIV, the virus that causes AIDS, are not aware of it, according to a new report by government health officials that zeroes in on one of the remaining hot spots of HIV infection in America.

Released on Tuesday by the U.S. Centers for Disease Control and Prevention, the report found young people ages 13 to 24 account for 26 percent of all new HIV infections in the United States.

"The data are stark and worrying," Dr. Kevin Fenton, director of the National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention at the CDC, said in a telephone interview.

In 2010, 72 percent of the estimated 12,000 new HIV infections in young people occurred in young men who have sex with men, and nearly half of new infections were among young, black males.

"We are particularly concerned about what is happening with HIV among young black and bisexual men," Fenton said.

Fenton said the proportion of young people infected with HIV has remained relatively stable during the last few years, but infection rates appear to be increasing in these populations.

And because many of the newly infected gay or bisexual males are just beginning to explore their sexuality, stigma and homophobia are making HIV testing and treatment far more challenging.

Only 22 percent of sexually active high school students in the United States have ever been tested for HIV, and only 35 percent of people ages 18 to 24 have been tested.

According to the report, which looked at risk behaviors among high school students in 12 states and in nine large urban school districts, young gay and bisexual men are significantly less likely to use condoms, they are more likely to drink alcohol or use drugs before sex, and they are more likely to have four or more partners during their lifetime compared with young men who had sex only with females.

And because so few get tested, HIV infected people under age 25 are significantly less likely than those who are older to get and stay in care, and to have their virus controlled at a level that helps them stay healthy and reduce their risk of transmitting HIV to partners.

CDC also found that many young men who have sex with men are less likely than others to have been taught about HIV or AIDS in school.

To address some of the issues, the CDC is funding a program that targets both the at-risk youths and the homophobia and stigma in the community that drives them underground.

In September, Georgia, a state where new HIV infections among those 13 to 24 years old exceed the national average - accounting for as many as one-third of all new HIV infections - won a grant as part of a pilot project to find better ways of targeting these at-risk youth.

"We think that it's really critical that the discussions we have about HIV prevention and access to HIV become fully integrated into the social fabric of the youth culture," Dr. Melanie Thompson of the Georgia Department of Public Health said in a telephone interview.

The Care and Prevention in the United States (CAPUS) project is a three-year program led by the CDC and other government agencies aimed at reducing HIV and AIDS among racial and ethnic minorities in the United States.

The program focuses on addressing social, economic, clinical and structural factors influencing HIV health outcomes.

"We are just beginning," Thompson said, adding that the program would focus specifically on the lives of young men who have sex with men and the barriers to testing and treatment.

To address stigma and bullying in the community, the program would feature training in which straight leaders in the faith community, business leaders, and entertainers learn about stigma and how it affects HIV in their community.

"It is a huge challenge, but I think if we do this from the point of view of trying to end an epidemic that is decimating our young people, and do it in a way that is science-based, I think we can make progress," she said.