Human T-Lymphotropic Virus Type 1 and Type 2 Seroprevalence, Incidence, and Residual Transfusion Risk Among Blood Donors in Brazil During 2007-2009

Human T-lymphotropic virus type 1/2 (HTLV-1/2) infection is endemic in Brazil but representative donor prevalence and incidence data are lacking. All blood donations (2007-2009) from three blood centers in Brazil were studied. Samples reactive on one HTLV screening test (ETA) were retested with a different ETA; dual ETA reactivity correlated strongly with a confirmatory Western blot. Prevalence, incidence, and residual transfusion risk were calculated. Among 281,760 first-time donors, 363 were positive for HTLV on both EIAs (135 per 10(5), 95% CI 122-150). Prevalence differed considerably by region, from 83 to 222 per 10(5). Overall incidence rate was 3.6/10(5) person-years and residual transfusion risk was 5.0/10(6) per blood unit transfused. The logistic regression model showed significant associations with: age [adjusted odds ratio (aOR) = 5.23 for age 50+ vs. <20], female sex (aOR = 1.97), black (aOR = 2.70 vs. white), and mixed skin colors (aOR = 1.78 vs. white), and inversely with education (aOR = 0.49, college vs. less than high school). HTLV testing with a dual-ETA strategy is feasible and can be useful in areas with low resources. Incidence and residual risk of HTLV-1 transmission by transfusion were relatively high and could be reduced by improving donor recruitment and selection in high prevalence areas. Blood center data may contribute to surveillance for HTLV infection.