Risk factors for HIV-2 seropositivity among older people in Guinea-Bissau. A search for the early history of HIV-2 infection

Because the seroprevalence of HIV-2 has been shown to be high in older age groups, we conducted a survey of all persons aged 50 years or over in two districts in Bissau, investigating the presence of HIV antibodies and possible risk factors for HIV infection with a particular emphasis on age, the impact of the war of independence (1963-74), traditional marital and extramarital sex patterns, blood contact and contact with monkeys. In 670 participants, the HIV-2 prevalence was 14.3%; 16.1% in women and 12.3% in men. The HIV-1 prevalence was only 0.5% (3/670). The HIV-2 prevalence peaked for men in the 60-69 years age group, and for women in the 50-59 years age group, declining markedly in the following age group for both men and women (OR = 0.09 (0.01-0.51), OR = 0.37 (0.15-0.82), respectively). This pattern could be due to differential mortality for HIV-2 infected individuals or to a cohort effect for a generation who were sexually active at the time of the war of independence in the 1960s and early 1970s in Bissau. Supporting the link with the colonial army, women who had had sex with a white man had a higher seroprevalence (OR = 3.63 (1.12-11.24)). The ethnic group indigenous to Bissau city had a much lower prevalence, but demographic and cultural risk factors such as marital status, religion, education and having lived outside Bissau were not associated with HIV-2. In the multivariate analyses for women, variables related to extramarital sex or prostitution (having sex with a white man, having lived in Senegal, not living with husband, and not marrying first sexual partner) were associated with higher risk. For men, previous spouses who had died or had divorced were associated with higher prevalence. Having married the first sexual partner was protective against HIV-2 infection for both men (OR = 0.29 (0.09-0.76)) and women (OR = 0.19 (0.04-1.00)). Hospitalizations, possibly due to transfusions, tended to be associated with higher risk, but only for women (OR = 1.83 (0.97-3.48)). The focus of the HIV-2 epidemic in Guinea-Bissau is likely to be endogenous, and the war of independence and the colonial army with its associated prostitution may have played an important part in propagating the virus.