Only 28 percent of 1.2 million Americans living with HIV have the infection under control, increasing the risk that they will spread the disease to others, U.S. health officials said Wednesday. A big part of the problem is that one in five U.S. adults infected with HIV don\'t know it. People can be infected with the AIDS virus for years without developing symptoms. Of those who are aware, only half receive ongoing medical care and treatment, the U.S. Centers for Disease Control and Prevention said in its report on HIV in America. CDC\'s report, released ahead of World AIDS day on Dec. 1, focuses on increasing rates of HIV testing and treatment. It follows new global AIDS priorities set by Secretary of State Hillary Clinton focusing on HIV-fighting drugs as a way of preventing new infections that could bring the goal of \"an AIDS-free generation\" within reach. \"It\'s now very clear that we have the tools to stop HIV in an individual and to stop the spread of HIV in a community,\" CDC Director Dr. Thomas Frieden said. \"We also know that taking treatment for HIV can prevent people from progressing to AIDS and from developing many of the serious complications of HIV, which unfortunately does remain an incurable infection,\" Frieden said. Recent studies have shown that suppressing the virus through treatment reduces the spread of HIV to partners by as much as 96 percent. But \"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,\" said Frieden. To reach groups at the greatest risk, the CDC is launching a new campaign urging regular testing for black gay and bisexual men, a population in which both HIV and syphilis infections continue to rise. While the number of Americans newly infected with HIV remained stable between 2006 and 2009, infections rose nearly 50 percent among young black gay and bisexual men, according to a CDC report released in August. Men who have sex with men -- which includes openly gay and bisexual men and those who do not identify themselves as gay or bisexual -- remain most heavily affected. While this group represents 2 percent of the overall U.S. population, they accounted for 61 percent of all new HIV infections in 2009.