Some 2.3 percent of 8,500 poor heterosexuals living in cities with high rates of HIV infection tested positive for the virus that causes AIDS, and nearly half of those who were infected said they had never had an HIV test before the study, U.S. health officials said on Thursday.

The findings by the Centers for Disease Control and Prevention underscore the links between poverty and HIV infection in the United States, where up to 44 percent of new infections are clustered in 12 major cities, including Chicago, Washington, New York and Los Angeles.

The study, published in the CDC's Mortality and Morbidity Weekly Report, involved a sampling of nearly 8,500 heterosexuals in 21 cities.

For the study, researchers analyzed 2010 data on heterosexuals in areas with a high AIDS burden who were considered to have low-socioeconomic status, which they defined as having an income below the federal poverty level or no more than a high school education.

More than 70 percent of participants were African American.

Of those tested, 197, or 2.3 percent, were infected with HIV, with highest rates of infection occurring among Blacks, those who reported using crack cocaine or those who exchanged sex for money or drugs.