Dr. Angela L. Hernandez of the Centers for Disease Control and Prevention in Atlanta said people who are unaware of their HIV infection might not change their behavior to reduce the risk for transmission and will not be linked to care, resulting in worse health outcomes.
"Enhanced efforts are needed to increase annual HIV testing for populations at high risk for HIV infection to increase early detection," a report by the CDC said.
CDC researchers analyzed data on people age 13 and older with a new diagnosis of HIV infection during 2006 to 2009 from 18 jurisdictions participating in HIV incidence surveillance.
The study found among adults and adolescents for whom previous HIV testing history information was available, 41 percent were diagnosed with HIV infection at their first HIV test, and 59 percent had a negative test at some point before HIV diagnosis, the report said.
Groups with the highest percentage of persons testing HIV-negative less than 12 months before HIV diagnosis included those aged 13-29 years at 33 percent, males with HIV transmission attributed to male-to-male sexual contact at 29 percent and whites at 28 percent.
The findings were published in the CDC's Morbidity and Mortality Weekly Report.