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) carrier and how horizontal transmission affects the prevalence of HTLV-1 carrier in pregnant Japanese women in 2019. We requested 2,214 obstetrical facilities to provide information of HTLV-1 tests in pregnant women who delivered in 2019. The estimated number of HTLV-1 carrier in pregnant Japanese women was 952. At least 10% or more of the HTLV-1 carriers were those due to horizontal transmission.