Determination of human T lymphotropic virus type by polymerase chain reaction and correlation with risk factors in northern California blood donors.

To determine the relative prevalence of human T lymphotropic virus (HTLV) types I and II, type-specific polymerase chain reaction (PCR) was done on seropositive northern California blood donors. From October 1988 through March 1990, 67 (0.055%) of 122,517 blood donors had confirmed HTLV antibody. Seropositive donors were more likely to be middle-aged, female, and nonwhite than the overall donor base. PCR of samples from 30 HTLV-seropositive donors yielded 19 (63%) with HTLV-II and 9 (30%) with HTLV-I; 2 (7%) were repeatedly negative by PCR. HTLV-I-infected subjects had ancestry (n = 3), sexual contact (n = 3), or paternal military service in (n = 1) Japan or the Caribbean. HTLV-II carriers reported past intravenous drug abuse (n = 3) or sex with a drug user (n = 11). Two carriers of each type reported previous blood transfusions, and 1 HTLV-II carrier was a dentist with no other risk factors for retroviral infection.