Age at second sex: a determinant of HIV transmission

Emma Slaymaker, London School of Hygiene and Tropical Medicine (LSHTM)
Nuala McGrath, London School of Hygiene and Tropical Medicine (LSHTM)

Age at first sex marks the start of an individual’s exposure to HIV infection, the acquisition of a second partner marks the point at which that individual could transmit infection. Unlike age at first sex, progression to a second sexual partner is not well documented. We describe this transition in selected sub-Saharan African countries using data from the Africa Centre Demographic Surveillance System (South Africa), the Masaka District Cohort Study (Uganda) and Demographic and Health Surveys (Tanzania, Uganda, Zimbabwe). From DHS data, standardised for age, men were more likely to have had a second partner than women (70% v. 50% in Tanzania, 70% v. 46% in Uganda; 62% v. 27% in Zimbabwe). By ages 45-49, around 90% of men had had more than one partner, compared to 60% of women in Tanzania and Uganda and 36% in Zimbabwe. A substantial proportion of women have no potential to transmit infection.