Most HIV
infections linked to people unaware they carry the virus

Up to 70% of the 40,000 new HIV infections occurring in the United States each year are transmitted sexually by adults unaware they are infected with the virus, Centers for Disease Control and Prevention officials write in the journal AIDS. A mathematical model developed at the CDC shows that 54% to 70% of new U.S. HIV cases are transmitted through sexual activity by people who are infected but have not been diagnosed as HIV-positive.

According to the CDC, there are approximately 1.1 million HIV-positive Americans, but one quarter of them--more than 250,000--are unaware they have the virus. Previous studies also have shown that HIV-positive people who are unaware they are infected are more than twice as likely to engage in high-risk sexual activities than HIVers who've been diagnosed, putting their sex partners at risk of infection.

"Our results indicate that the HIV-positive-unaware group contributes disproportionately to [sexually acquired new HIV] infections relative to their percentage of the HIV-positive population in the U.S.A.," the study's authors write. The data shows the HIV transmission rate among this group is 3.5 times higher than among HIV-positive people who've been tested and diagnosed.

CDC officials say the study reinforces the agency's belief that encouraging HIV antibody testing is one of the keys in controlling the U.S. HIV epidemic. Targeted HIV antibody testing campaigns--including those aimed at such high-risk groups as gay men, African-Americans, and injection-drug users--as well as promoting routine HIV antibody testing in hospitals, clinics, and doctor's offices are important steps to take to identify people who are unaware they're infected and lower transmission rates, the CDC says. (The Advocate)