Heterosexual transmission of HIV in Africa: an empiric estimate.

For more than a decade, most experts have assumed that more than 90% of HIV in African adults results from heterosexual transmission. In this exercise, we show how data from studies of risk factors for HIV can be used to estimate the proportion from sexual transmission, and we present our estimates. Calculating two ways from available data, our two point estimates - we do not estimate confidence intervals - are that 25-29% of HIV incidence in African women and 30-35% in men is attributable to sexual transmission; these estimates assume 10% annual epidemic growth. These findings call for reconceptualization of research to more accurately assess routes of HIV transmission.