OBJECTIVE: To assess the efficacy of transmission of HIV-1 within married couples in rural Uganda according to the sero-status of the partners. DESIGN: Estimation of HIV incidence rates for 2200 adults in a population cohort followed for 7 years comparing male-to-female with female-to-male transmission and sero-discordant with concordant sero-negative couples. METHODS: Each year, adults (over 12 years of age) resident in the study area were linked to their spouses if also censused as resident. The HIV sero-status was determined annually. RESULTS: At baseline 7% of married adults were in sero-discordant marriages and in half of these the man was HIV-positive. Among those with HIV-positive spouses, the age-adjusted HIV incidence in women was twice that of men (rate ratio (RR) = 2.2 95% confidence interval (CI) 0.9-5.4) whereas, among those with HIV-negative spouses, the incidence in women was less than half that of men (RR = 0.4, 95% CI 0.2-0.8). The age-adjusted incidence among women with HIV-positive spouses was 105.8 times (95% CI 33.6-332.7) that of women with HIV-negative spouses, the equivalent ratio for men being 11.6 (95% CI 5.8-23.4). CONCLUSION: Men are twice as likely as women to bring HIV infection into a marriage, presumably through extra-marital sexual behaviour. Within sero-discordant marriages women become infected twice as fast as men, probably because of increased biological susceptibility. Married adults, particularly women, with HIV-positive spouses are at very high risk of HIV infection. Married couples in this population should be encouraged to attend for HIV counselling together so that sero-discordant couples can be identified and advised accordingly.

JOURNAL ARTICLE Adolescence Adult Cohort Studies Female Human HIV Infections/EPIDEMIOLOGY/*TRANSMISSION *HIV Seronegativity *HIV Seropositivity *HIV-1 Incidence Male *Marital Status Middle Age Rural Population Sex Behavior *Sexual Partners Support, Non-U.S. Gov't Uganda/EPIDEMIOLOGY

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