The sharpest increase in HIV diagnoses is occurring among young black men who have sex with men (MSM), notably those in their teens and early 20s. The new data were reported yesterday by the U.S. Centers for Disease Control and Prevention (CDC) at the National HIV Prevention Conference in Atlanta.

To better understand HIV transmission trends among different populations of MSM, Joseph Prejean, PhD, from the CDC, and his colleagues evaluated data from the national HIV/AIDS Reporting System, which collects data on HIV and AIDS diagnoses in 33 states with confidential names-based reporting systems. Adult and adolescent cases of HIV and AIDS among black, white and Hispanic MSM diagnosed between January 2001 and December 2005 were included in the analysis.

Prejean’s team grouped the MSM according to their year of birth to establish trends in new HIV diagnoses by age. For instance, men who were born in 1970 and were diagnosed with HIV in 2001 would have been 31 at the time of their diagnosis. Men born in 1974 but diagnosed in 2005 would also have been 31 at the time of their diagnosis.

They found that men born between 1965 and 1969 had the highest rate of new HIV diagnoses in every year between 2001 and 2005, however the rate among men born during those years remained relatively stable over the four-year period.

Among black MSM born between 1975 and 1979 and between 1980 and 1984, however, the rate of new HIV diagnoses increased dramatically between 2001 and 2005. In fact, by 2005, the rate of HIV diagnoses among black MSM born between 1980 and 1984 was nearly equal to the men with the highest rate overall—those born between 1965 and 1969. Rates of new diagnoses among white and Hispanic men born between 1980 and 1984 did not increase nearly as dramatically.