To evaluate the risk of transfusion-related transmission of HTLV-I in Jamaica, a prospective study was initiated, prior to availability of a licensed HTLV-I serological screening assay. This information would prove useful in formulating strategies for blood-donor screening. We followed I I8 pre-transfusion HTLV-
I-negative transfusion recipients at monthly intervals
posttransfusion for I year. Laboratory and questionnaire data were obtained at each visit to evaluate the clinical and immunological status of recipients. Cumulative incidence of HTLV-I seroconversion was estimated and risk-factor data associated with seroconversion among 66 HTLV-I-exposed transfusion recipients were analyzed. Seroconversion occurred in 24/54 (44%) of recipients of HTLV-I-positive cellular blood components, O/ I2 recipients of positive non-cellular donor units and 0/52 recipients of HTLV-I-negative donor units. Significant risk factors associated with recipient seroconversion were receipt of a seropositive cellular blood component stored for less than one week [odds ratio (OR) = 6.34,95% confidence interval (CI) = I .83 to 2 I .92], male sex (OR = 4.79,95% CI = I. I5 to 20.0) or use of immunosuppressive therapy at time of transfusion (OR = 12.20, 95% CI = 0.95 to 156). Risk of blood-borne infection per person per
year in Jamaica was estimated to be 0.009%. Our results confirm that blood transfusion carries a significant risk of MTLV-I transmission and that screening of donor blood effectively prevents HTLV-I seroconversion. Recipients at greatest risk for seroconversion were those who required multiple transfusions or who were receiving immunosuppressive therapy ;at the time of transfusion. These patients should be given priority in receiving selectively screened blood components, if iuniversal blood-donor screening for HTLV-I is not possible.