To test the hypothesis that the seroprevalence of HTLV-1 is male predominant during adolescence.
The presence of HTLV-1 antibody in 272,043 blood samples donated to a regional blood bank in an HTLV-1 high-endemic region was assessed.
The entire population of female donors had a significantly higher seroprevalence compared to males (2.05 % and 1.80 % , respectively, p < 0.0001). However, compared with male donors, the carrier rate for female donors was lower for the youngest subgroup (16–19 years, p = 0.0011); was similar for the next two age subgroups (20–29 years and 30–39 years); and was significantly higher for the last two age subgroups (40–49 years and over 50–64 years, both p < 0.0001). In general, older age subgroups led to higher seroprevalence in both genders.
HTLV-1 infection is more common for males until after age 20, when male to female sexual transmission becomes likely. This suggests that mother-to-child transmission is more common for males.