RESUMEN
HTLV-I and HTLV-II are two related retroviruses that are transmitted by sexual contact, breast feeding, blood transfusion and needle sharing. In this study the prevalence of HTLV-I and HTLV-II was evaluated in voluntary blood donors as a measure of the infection in the general population. Samples were tested by a gelatine particle agglutination test and repeatedly reactive samples were confirmed by Western blot tests (WBT), enriched with recombinant rgp21, rgp46I y rgp46II proteins, which differentiates HTLV-I and HTLV-II antibodies. Of 19,426 samples, 40 were repeatedly reactive by particle agglutination (0.21 percent). When analyzed by WBT, 6 met the criteria for HTLV-I (0.036 percent), 2 for HTLV-II (0.01 percent) and 1 for HTLV-I/II, 13 samples were indeterminate and 18 were negative. The prevalence is low and comparable to that from non endemic countries. Screening for anti HTLV-I/II antibodies is necessary to prevent transmission through blood transfusions.