Background:  In South Africa, 1 in 5 women 18 to 24 years of age is infected with HIV compared with <1% of young women in the United States. Since the beginning of the AIDS epidemic, researchers have searched for explanations for the great variation in HIV prevalence between Africa and the West. Many of the explanations for the heterosexual spread of HIV in Africa have attributed the epidemic to exotic sexual behaviors and cultures that promote promiscuity.

Methods:  Using data from nationally representative, population-based studies of adolescents in the United States (the National Longitudinal Study of Adolescent Health) and South Africa (the Reproductive Health and HIV Research Unit National Youth Survey), we aimed to describe the sexual behaviors of young people aged 18 to 24 years to determine whether differences may help explain the enormous disparity in HIV prevalence. The sampling frame and weights of each dataset were taken into account using appropriate statistical techniques, using Stata9. 

Results:  The majority of youth in the United States and South Africa report ever having had vaginal sex, 87.9% and 86.0% of American young men and women, respectively, compared with 84.4% and 81.9% of South African adolescent men and women. The mean number of lifetime partners reported were 5.7 and 2.3 for United States and South African adolescent women, respectively, and 7.1 and 4.3 for United States and South African young men, respectively. The mean age at coital debut was reported to be 16.3, 17.4, 16.4, and 16.7 for American females, South African females, American males, and South African males, respectively. Young men in both countries reported using condoms more at last sex than their female counterparts; in the United States, 36.1% of young women and in South Africa 45.4% of young women reported using a condom at last sex while 48% of US and 58% of South African adolescent men did so. 

Conclusions:  Overall, the sexual behaviors of young Americans and South Africans are not that different and do not appear to explain the enormous disparity in the HIV epidemics in the 2 countries. In fact, American youth report slightly riskier sexual behaviors than their South African counterparts. While sexual behavior is a key determinant of becoming infected with HIV, factors that affect the probability of HIV transmission (ie, viral load, sexually transmitted infections, circumcision) and the existing background prevalence of HIV are likely the key drivers for the continued spread of HIV in South Africa.