Recent Prevalence of Human T-cell Leukemia Virus Type 1 Carrier Associated with Horizontal Transmission in Pregnant Japanese Women

The current study was conducted to examine the number of human T-cell leukemia virus type 1 (HTLV-1) carriers and how horizontal transmission affected the prevalence of HTLV-1 carriers among pregnant Japanese women in 2019. We requested 2,214 obstetrical facilities to provide information on HTLV-1 tests for pregnant women who delivered in 2019. The estimated number of HTLV-1 carriers among pregnant Japanese women was 952. At least 10% or more of the carriers acquired HTLV-1 through horizontal transmission.