Geographical clustering of high risk sexual behaviors in "hot-spots" for HIV and sexually transmitted infections in Kwazulu-Natal, South Africa.

We investigated geographical variations of three sexually transmitted infections (STIs) namely chlamydia, gonorrhea and syphilis in the greater Durban area, so as to optimize intervention strategies. The study population was a cohort of sexually active women who consented to be screened in one of three biomedical studies conducted in Durban. A total of nine local regions collectively formed three clusters at screening, five of which were previously defined as HIV hot-spots. STI cases were geo-coded at the census level based on residence at the time of screening. Spatial SaTScan Statistics software was employed to identify the areas with a disproportionate prevalence and incidence of STI infection when compared to the neighboring areas under study. Both prevalence and incidence of STIs were collectively clustered in several localized areas, and the majority of these locations overlapped with high HIV clusters and shared the same characteristics: younger age, not married/cohabitating and multiple sex partners.