Between 2006 and 2009, new HIV infections have remained relatively stable in the United States, despite advances to treat and prolong life for people living with AIDS.

Each year, approximately 50,000 people become infected with HIV, according to data from the Centers for Disease Control and Prevention. The numbers are consistent to infection rates over the past decade.

Some researchers believe infections fluctuated in the 80s and 90s, eventually plateauing in the early 2000s, according to the New York Time. Others are optimistic about research advances that make testing cheaper and more available to people who need it.

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So which risk groups are still at the highest risk of HIV transmission and why?

The hardest hit group is young, black men, says the report. Both gay and bisexual black men have the highest infection rates, with their cases comprising 61 percent of all new infections in 2009 (although they only represent 2 percent of the U.S. population).

Unfortunately, these are the same groups that may lack health insurance and hide their lifestyles from friends and family. Add the risks associated with unprotected sex, and it becomes clear that getting tested or receiving routine medical attention is anything but easy.

Minorities are still hard hit by HIV, which means the chances of coming in contact with the virus are higher among people who have sex with others in their same community.

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On the other hand, HIV prevention has been the most successful for pregnant women or recent mothers who risk passing the virus along to children through breast milk. Spreading HIV via drug needles has also drastically fallen with time.

The data highlights the need to hone in on targeting prevention programs to some groups more than others. Though this has always been the case, now officials know that prevention is more problematic than previously thought for certain groups.

So far, practicing safe sex with condoms is the best way to limit HIV transmission, but options such as pre-exposure prophylaxis have shown promise for men who have sex with men and have been exposed to HIV. The idea is to give patients antiretroviral medications to possibly prevent the virus from taking hold and multiplying in the bloodstream.

The analysis is featured in this month’s issue the journal PLoS ONE.

An enlarged and colored micrograph of HIV on a lymphocyte cell. Photo by C. Goldsmith, P. Feorino, E. L. Palmer, W. R. McManus/CDC/Wikimedia Commons