SHARECOMMENTMORE

ATLANTA -- There's some good news from the AIDS front: Fewer needle drug users are testing positive for HIV.

The Centers for Disease Control and Prevention released the study Thursday.

Officials say the rate of drug users contracting HIV has dropped by half since the 1990s. The decline may be related to a growth in needle exchange programs.

More than 10,000 drug users in 20 metropolitan areas were surveyed and tested for HIV in 2009. About 1 in 10 tested positive for the virus; in the '90s, roughly 1 in 5 did.

The study also found that only about half of infected drug users know they carry the AIDS virus.

Addicts who inject heroin, cocaine or other drugs have been one of the groups hit hardest by AIDS.