Epidemiology: Sexual transmission of HIV in Africa

The human immunodeficiency virus (HIV) epidemic in sub-Saharan Africa continues to grow at an alarming rate, with 3.5 million people infected last year alone. It has recently been proposed that heterosexual transmission cannot account for more than 35% of HIV incidence in this region, and that parenteral transmission, probably through unsterile medical practices, is the main route of infection. A key prediction of this hypothesis is that the epidemic history of HIV in sub-Saharan Africa is similar to that of other blood-borne pathogens. To test this, we compared prevalence estimates of HIV with those of hepatitis C virus (HCV), which has a far greater rate of parenteral than sexual transmission. We show that HIV and HCV have such different epidemic histories in sub-Saharan Africa that parenteral transmission is unlikely to be the main source of HIV infection.