Prevalence of HIV-1 infection in Zanzibar: Results from a national HIV-1 serosurvey 2002

Abstract

Objective: To determine the prevalence of HIV-1 infection in Pemba and Zanzibar islands
Methods: We used an interviewer-administered questionnaire that consisted of pre-coded and open-ended questions consisting of 29 items. The questionnaire was developed in English and translated into Swahili language before use. The questionnaire was pilot tested and modified before use. A total of 30 Shehias were randomly selected for the survey out of a total of 248 Shehias. A Shehia is the smallest government admionistrative unit in Pemba and Zanzibar that consists of two to three villages. The study sample was obtained through cluster random sampling of 76 households from each Shehia. Informed consent was sought from the Head of household and from each potential eligible participant. Eligibililty criteria included all persons aged 12 years and above who slept overnight in the selected household at the time of the study. Exclusion criteria included non-residents of Zanzibar and Pemba such as tourists. Informed consent from persons below the age of 18 years were witnessed and ratified by their parents, guardians, caretakers or neighbours. All consenting participants were included in the study sample. Blood sports were collected using filters and tested for HIV-1 using ELISA test at the Zanzibar Reference Laboratory. Samples found positive for ELISA were subjected to a 2^nd ELISA test.
Results: The total number of persons who participated in the survey was 5852 out of 5868 eligible persons giving the overall response rate of 99.7%. Of the 5852 persons who participated in the survey, 41% (N= 2414) were males and 59% N=3455) were females. The overall mean age of the study population was 30.4 years with age ranging from 12-65 years. The overall prevalence of HIV-1 infection was 0.6% with more women being significantly affected than men (0.9% versus 0.2%; adjusted OR = 2.88, 95% CI = 1.16-7.12). Of the 5852 persons who participated in the survey, 5.7% admitted having had casual partner in the past 6 months and of these 19.6% reported having used a condom during the most recent casual sex.
Conclusion: We conclude that HIV-1 infection in Zanzibar is still low and women are more affected than men.

Key words: HIV-1 infection, Condom use, Population-based survey, Risky sexual behaviour, Zanzibar