Seroincidence of human T-lymphotropic virus type I infection and characterization of seroconverters in Jamaican food handlers.

In a prospective study of food handlers in Jamaica, we estimated the age- and sex-specific seroincidence of human T-lymphotropic virus type I (HTLV-I) infection. Of 682 sexually active adults (132 males and 550 females) who were initially seronegative, 12 (1 male and 11 females) seroconverted over 8 years of follow-up. The seroincidence was 1.2 per 1,000 person-years for males and 3.2 per 1,000 person-years for females. The age-standardized incidence was 1.8 times higher for females than for males (P = 0.55). Within a median of 4 years after seroconversion, the median HTLV-I provirus load was 500 copies/105 cells, and the median antibody titer was 1:3109. Four of 12 seroconverters developed antibody to the Tax regulatory protein. HTLV-I infection in this population occurred at a rate comparable with that described for a Japanese cohort. Provirus load, titer and appearance of antibody to the Tax regulatory protein were typical of chronic carriers within a few years of seroconversion.