Concomitant carriage of hepatitis B virus and human T-lymphotropic virus type I among blood donors in Kitakyushu, Japan.

The seroprevalence of hepatitis B surface antigen (HBsAg) by gender and age and of human T-lymphotropic virus type I (HTLV-I), and their concomitant carriage was examined among blood donors at the Kitakyushu Red Cross Blood Centre in the fiscal year of 1988. The positive rates of HBsAg among males were consistently higher than those of females; the peaks were detected in male donors aged 30-39 years and in females aged 40-49 years. Declining seropositive rates in individuals aged 50 years or over were observed for both genders. Self-selection due to chronic HBV infection may partly account for such tendencies. On the other hand, the prevalence rates of anti-HTLV-I antibodies among males were uniformly lower than those of females, which must be attributable to male-to-female transmission of HTLV-I via sexual contact. Elevated positive rates in proportion to age were noted for both genders, which may be explained in part by birth cohort effect. The seropositive rates of HBsAg among HTLV-1 carriers were not statistically different from those of non-HTLV-I carriers. Conversely, the prevalence of antibodies to HTLV-I was unrelated to the status of seropositivity of HBsAg.