Migration, sexual behaviour, and HIV risk: a general population cohort in rural South Africa.

backgroundIncreased sexual risk behaviour and HIV prevalence have been reported in migrants compared with nonmigrants in sub-Saharan Africa. We investigated the association of residential and migration patterns with sexual HIV risk behaviours and HIV prevalence in an open, general population cohort in rural KwaZulu-Natal, South Africa.

methodsIn a mainly rural demographic surveillance area in northern KwaZulu-Natal, South Africa, we collected longitudinal demographic, migration, sexual behaviour, and HIV status data through household surveillance twice per year and individual surveillance once per year. All resident household members and a sample of non-resident household members (stratified by sex and migration patterns) were eligible for participation. Participants reported sexual risk behaviours, including data for multiple, concurrent, and casual sexual partners and condom use, and gave a dried blood spot sample via fingerprick for HIV testing. We investigated population-level differences in sexual HIV risk behaviours and HIV prevalence with respect to migration indicators using logistic regression models.

findingsBetween Jan 1, 2005, and Dec 31, 2011, the total eligible population at each surveillance round ranged between 21 129 and 22 726 women (aged 17-49 years) and between 20 399 and 22 100 men (aged 17-54 years). The number of eligible residents in any round ranged from 24 395 to 26 664 and the number of eligible non-residents ranged from 17 002 to 18 891 between rounds. The stratified sample of non-residents included between 2350 and 3366 individuals each year. Sexual risk behaviours were significantly more common in non-residents than in residents for both men and women. Estimated differences in sexual risk behaviours, but not HIV prevalence, varied between the migration indicators: recent migration, mobility, and migration type. HIV prevalence was significantly increased in current residents with a recent history of migration compared with other residents in the study area in men(adjusted odds ratio 1·19, 95% CI 1·07-1·33) and in women (1·18, 1·10-1·26).

interpretationLocal information about migrants and highly mobile individuals could help to target intervention strategies that are based on the identification of transmission hotspots.Funding Wellcome Trust.