Transmission of retroviruses by transfusion of screened blood in patients undergoing cardiac surgery.

We determined the rates of seroconversion to human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus Type I (HTLV-I) in a cohort of patients receiving transfusions of blood components screened for antibody to HIV-1. Preoperative and postoperative serum samples were collected from 4163 adults undergoing cardiac surgery who received 36,282 transfusions of blood components. The postoperative samples from all patients were tested for serologic evidence of HIV-1 infection, and those that were positive were compared with the corresponding preoperative samples. One case of HIV-1 transmission by transfusion of screened blood components was identified; two preexisting HIV-1 infections were found. Samples from 2749 patients were tested similarly for serologic evidence of HTLV-I infection; these patients received 20,963 units of blood components. Five new cases and two preexisting cases of HTLV-I infection were detected. The observed risk of HIV-1 transmission by transfusion was 0.003 percent per unit; the risk of HTLV-I transmission was 0.024 percent per unit. We conclude that there is a very small risk of HTLV-I infection from transfused blood products that have been screened for antibodies to HIV-1, but that it is nearly 10-fold higher than the risk of HIV-1 infection.