Human T-lymphotropic virus (HTLV) types I and II infection in sexual contacts and family members of blood donors who are seropositive for HTLV type I or II. American Red Cross HTLV-I/II Collaborative Study Group.

Interviews and laboratory testing were conducted for 168 contacts referred by former blood donors identified as seropositive for antibody to human T-lymphotropic virus type I (HTLV-I) or type II (HTLV-II). Thirty-two (28%) of 114 heterosexual contacts of seropositive donors, including 12 women and 20 men, were found to be antibody positive. None of 40 offspring (except one adult man who reported sexual contact in Puerto Rico) or 14 other (nonspousal) family members were seropositive. Thirty-one of the seropositive contacts were typeable as having either HTLV-I (52%) or HTLV-II (48%). Assessment of couples found that the median duration of the sexual relationship was significantly longer (p = 0.03) for those in which both partners were infected than in discordant pairs. Analysis of risk history data for 22 infected couples revealed that, in three cases, risk factors (Japanese ancestry or sexual contact with an injecting drug user) could be identified in the women, but not in their male partners. Among couples in which the male had the greater risk history, the risk factor was either a history of transfusion, birth or sexual exposure in an endemic area, or injected drug use. Counseling strategies for individuals with HTLV-I or HTLV-II infection should take into account the relatively high seroprevalence in their partners and should address the potential for sexual transmission in both directions.