Risk factors for incident human immunodeficiency virus infection in South African blood donors.

Background and objectives: Recruiting blood donors among a population with a high human immunodeficiency virus (HIV) burden requires detailed information on HIV risks. We studied demographic and behavioural risk factors for incident HIV infection among blood donors in South Africa.

Materials and methods: We conducted a case-control study. Incident HIV was defined as HIV antibody negative and RNA positive, or concordant serology and RNA positive with a limiting antigen avidity assay optical density of <1.5. Cases were matched to infection-negative controls (ratio 1:3) on race, age and geography. Risk factors in the 6 months before donation were ascertained by audio computer-assisted self-interview. Data were fitted using separate multivariable logistic regression models for males and females.

Results: From April 2014 to March 2017, we enrolled 323 people with incident HIV and 877 controls. Among women, incident HIV was associated with sex with a person living with HIV (PLWH) or unknown HIV status, multiple male sex partners, never or occasional condom use, anal preparation before sex, first-time donor status and referral to donation by a healthcare worker. Among men, incident HIV was associated with being aged 31-40 years, sex with a PLWH or unknown HIV status, multiple sex partners, more than four lifetime male sex partners, gay/bisexual identity, marriage or stable partnership, lower education, penetrative injury, occasional condom use and first-time or lapsed donor status. Some novel or indirect risks for incident HIV were also observed.

Conclusion: We confirmed the known sexual behaviours asked on the donor screening questionnaire. The findings highlight ongoing challenges in donor disclosure during selection and the importance of donor education.