HIV-1 incidence among male workers at a sugar estate in rural Malawi

Objectives: To determine incidence of HIV and associated risk factors in tw o cohorts of men working at a sugar estate in rural Malawi. Design: Prospective studies. Methods: After counseling and obtaining informed consent, male workers were tested for HIV-1 and syphilis. Baseline HIV-seronegative men were enrolled in two follow-up studies in 1994 and 1998, and were retested for HIV and s yphilis at G-month follow-up visits. Demographic, behavioral, and medical h istory was collected at baseline. Cumulative HIV incidence based on Kaplan- Meier methods was estimated. HIV incidence was also estimated per 100 perso n-years (p-y). Crude and adjusted rate ratios for the association of risk f actors with incident HIV infection were obtained using Cox proportional haz ards models. Results: HN prevalence was 24.3% among 1692 men screened in 1994 and 21.0% among 1349 men screened in 1998 (p < .03). HIV incidence was extremely high during 1994 to 1995 (17.1% for that 1-year period). Incidence dramatically declined in 1996, averaging about 3.5% per year from 1996 through 1999. Am ong men enrolled in the 1998 cohort, HIV incidence during 1998 to 1999 was 3.8%. After controlling for potential confounders reactive syphilis was ass ociated with a twofold risk of HIV acquisition in each cohort. Conclusions: Urgent preventive measures are needed to control the spread of HIV in this economically important occupational cohere. In addition to con ventional educational messages to reduce risky sexual behavior, treatment o f other sexually transmitted diseases should be considered.