SEXUAL-BEHAVIOR PATTERNS AND OTHER RISK-FACTORS FOR HIV-INFECTION IN RURAL TANZANIA - A CASE-CONTROL STUDY

Objective: To examine the association between HIV infection and patter ns of sexual behaviour and other risk factors in a rural Tanzanian pop ulation in a case-control study, nested within a randomized trial of i mproved sexually transmitted disease treatment. Methods: All HIV-posit ive patients from the baseline survey of the randomized trial were eli gible as cases. Cases (n = 338) and controls (a random sample of one i n eight HIV-negative persons; n = 1078) were interviewed about risk fa ctors for HIV infection using a structured questionnaire. Results: A s ignificantly higher HIV prevalence was found among men and women not c urrently employed in farming [men: odds ratio (OR), 2.08; women: OR, 3 .65], women who had travelled (OR, 3.27), educated women (OR, 4.51), a nd widowed/ divorced people compared with those currently married (men : OR, 3.10; women: OR, 3.54). Two spouse-related factors were signific antly associated with HIV, even after adjustment for the sexual behavi our of the index case: HIV was more prevalent in men with younger spou ses (P = 0.020 for trend) and in women married to men currently employ ed in manual work, office work or business (OR. 2.20). In women only, blood transfusions were associated with a higher HIV prevalence (OR, 2 .40), but only a small population attributable fraction (4%). There wa s an increased HIV prevalence associated with increasing numbers of in jections. Reported number of lifetime sexual partners was significantl y associated with HIV infection (women: OR, 7.33 if greater than or eq ual to 10 lifetime partners compared with less than or equal to 1; men : OR, 4.35 for greater than or equal to 50 compared with less than or equal to 1). After adjustment for confounders, male circumcision was a ssociated with a lower HIV prevalence (OR, 0.65; P= 0.11). Conclusions : In these rural communities, many HIV infections occur through sexual transmission. Some people are al high risk of HIV infection through l arge numbers of sex partners, whereas some are at risk through their s pouse or regular partner. The role of circumcision in HIV transmission is unclear. Commercial sex seems to play a negligible role in HIV tra nsmission in these communities. Our results confirm marked heterogenei ty in HIV risk, indicating the scope for risk reduction strategies.