Objectives To assess the burden of sexually transmitted infections (STIs) among HIV-positive South Africans in the period prior to antiretroviral therapy (ART) initiation compared with the period once on ART.

Methods We linked the clinic records of 1465 patients currently on ART to the electronic database which records all visits to city clinics. We used a mixed effects Poisson model to assess the relative rates of occurrence of treatment seeking for an STI in the periods prior to initiation of ART and while on ART.

Results We accumulated 4214 person-years of follow-up, divided nearly equally between the pre-ART and on-ART periods. The rate of treatment seeking for new STIs was 5.50 (95% CI 5.43 to 5.78) per 100 person-years, and individuals had on average a sevenfold higher rate of seeking treatment for STIs in the period prior to initiating ART (9.57 per 100 person-years) compared with the period once on ART (5.5 per 100 person-years) (adjusted rate ratio (RR) 7.01, 95% CI 4.64 to 10.59). Being male (RR 1.73, 95% CI 1.18 to 2.55) or younger (age <25) (RR 2.67, 95% CI 1.53 to 4.65) was associated with higher incidence of clinic visits for STI treatment, while advanced stage of HIV disease (WHO stage 4) (RR 0.33, 95% CI 0.15 to 0.69) was associated with lower incidence.

Conclusions The period prior to the initiation of ART is a critical period where increased attention should be focused on the detection and treatment of STIs. A successful effort to treat STIs in this period will likely reduce further HIV transmission and fits within a test-and-treat approach.