We included all eligible first-time blood donors at South African National Blood Service (SANBS) facilities for January 2012–September 2015, covering all provinces except Western Cape Province. We excluded those deferred from donation because of risk behaviors or poor health.

We screened blood donations individually for HIV RNA, HCV RNA, and HBV DNA by using the Procleix Ultrio Plus assay (Grifols, Barcelona, Spain) and serologically for HIV antibodies, HCV antibodies, and HBsAg by using Abbott Prism ChLia (Abbott, Delkenheim, Germany). We further tested serologic repeat–reactive but nucleic acid testing (NAT)–negative donations by using supplemental assays: HIV Western blot (Bio-Rad, Hercules, CA, USA); HCV InnoLIA (Innogenetics, Ghant, Belgium); or HBsAg neutralization (Roche, Pleasanton, CA, USA).

We calculated prevalences and derived odds ratios (ORs) and 95% CIs for associations from multivariable logistic regression by using SAS/STAT 9.4 (SAS Institute, Inc., Cary, NC, USA). Because of statistically significant interactions between sex and age and between sex and race (Technical Appendix 1), we built separate models for male and female donors.

During January 2012–September 2015, a total of 3,075,422 blood donations were made at SANBS facilities from repeat donors; 397,640 (13%) donations were from first-time donors, who were predominantly young and equally distributed by sex (Table). Approximately half of donors were black, one third white, and the remainder of Asian; South African Colored (SAC) (an admixed group made up of 5 source populations [African Khoisan, African Bantu, European, South Asian, and East Asian]); or unknown race/ethnicity.

Figure

Figure. Overall prevalence of HIV (A) and hepatitis B virus (B) in South Africa, by province, among persons making blood donations through the South African National Blood Service, January 2012–September 2015. Pink...

A total of 4,481 (1.13%) first-time donors were classified as HIV positive. Prevalence was highest (1.3%–1.9%) among persons 20–49 years of age, higher among female (1.4%) than male (0.8%) donors, and higher among those of black race/ethnicity (2.0%) than other races/ethnicities (Table). In logistic regression models (Technical Appendix 2), HIV infection was more strongly associated with older age among male donors than among female donors and more strongly with black and unknown race/ethnicity among female donors than among male donors (Technical Appendix 1). We observed a significant association between HIV and HBV infection in both sexes and a stronger association between HIV and HCV infection in female donors only. Compared with Gauteng Provence, HIV infection was associated with donation in Mpumalanga, KwaZulu-Natal, and Free State provinces for both sexes and with Eastern Cape Province for female donors and Northern Cape Province for male donors (Figure).

The 1.13% HIV prevalence among first-time blood donors in South Africa is much higher than that for high-income countries but lower than for many countries in sub-Saharan Africa, where HIV prevalence ranges from 3% to 5% (8). HIV prevalence among donors was substantially lower than that among the general adult population of South Africa (estimated at 18.8%), but similar demographic associations were observed (1,2). Geographic distributions of HIV infection were also generally similar to national data, although we found higher adjusted odds for HIV infection in Mpumalanga Province compared with KwaZulu-Natal Province (1). Incorporation of blood donor prevalence and incidence data might help to refine statistical models of the HIV epidemic, which have not performed well in some subgroups (2,9). In addition, blood bank testing for HIV includes men and older persons, who are not well-represented in current surveillance strategies (10).

A total of 2,638 (0.66%) first-time donors were classified as HBV-positive. HBV prevalence was 0.9%–1.3% among those 30–49 years of age, and only 0.2% among those <20 years of age (Table). HBV prevalence was 0.9% among male donors versus 0.5% among female donors, 1.1% among blacks, 0.5% among persons of SAC race/ethnicity, and 0.1% among whites. In the logistic regression models (Technical Appendix 2), HBV infection was more strongly associated with older age among men than among women and had a geographic distribution slightly different from that of HIV.

The HBV prevalence of 0.66% was substantially less than the median of 4.35% for all countries in Africa; however, lack of confirmatory testing might inflate the proportion for all of Africa (11). In our study, a 5-fold lower prevalence among donors <20 years of age compared with those 20–29 years of age is consistent with the implementation of HBV vaccination of infants in South Africa in 1995 and could be used to estimate vaccination coverage (3). Male donors appear to be at higher risk for chronic HBV infection, as reported in the United States (12).

Only 125 (0.03%) donors were confirmed positive for HCV infection. HCV prevalence was highest (0.4%) among those >60 years of age (0.04% among men, 0.02% among women) (Table). We observed little difference in HCV prevalence by race/ethnicity. In logistic regression models, HCV infection was associated with older age and with HIV co-infection among women only (Technical Appendix 2). Among men only, HCV was inversely associated with blood donation in Eastern Cape and KwaZulu-Natal Provinces.

Contrary to some reports, which included small studies and those lacking confirmatory testing (13), HCV infection appears to be rare among South Africa blood donors and, by extrapolation, its general population. The 0.03% blood donor prevalence we found is consistent with an older study (4) and much lower than the median of 0.86% for other countries in Africa (11). Reasons for this low prevalence are unclear but likely relate to the relative absence of injection drug use or other parenteral risk factors for HCV transmission. Further study of why South Africa has lower HCV prevalence than many countries in the world is warranted. One clue might be the predominance of infection among older and male persons, suggesting a possible birth cohort effect related to historical parenteral exposures (14).

Our study attests to the success of blood donor selection and screening: HIV prevalence was ≈18-fold lower and HBV prevalence 5-fold lower than that of the general population of South Africa. This difference is attributable to selection of low-risk and healthy donors and underrepresentation of blacks among blood donors. These biases need to be accounted for in extrapolating directly to the general population, but comparisons between donor subgroups or periods might still mirror population data. Prevalent infections in donors are detected by serologic testing, and blood products are discarded accordingly. To mitigate the risk posed by seronegative window period infections, SANBS performs routine individual donation NAT. This parallel serology and NAT testing has generated substantial data on HIV and HBV incidence, further contributing to public health surveillance (6).