Age and gender specific prevalence of HTLV-1

Abstract Background The seroprevalence of Human T-cell Leukemia Virus Type 1 (HTLV-1) is female predominant despite the higher incidence of Adult T-cell Leukemia (ATL) in males. If the mother-to-child transmission of HTLV-1 is more common for male infants than in female infants, longer exposure to the virus for males may explain the paradoxically higher incidence of ATL. Objectives To test the hypothesis that the seroprevalence of HTLV-1 is male predominant during adolescence. Study design 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. Results 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. Conclusions 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.