Abstract
BACKGROUND: In Japan, the risk of transfusion-transmitted hepatitis B virus (TT-HBV) infection has been reduced since 2014 by implementing individual donation nucleic acid amplification testing (ID-NAT). CASE REPORT: A male repeat blood donor in his 20s converted positive for HBV DNA and hepatitis B surface antigen. Red cell concentrate from his previous donation had been transfused into a woman in her 70s. Her serum showed HBV DNA positivity 62 days after transfusion. HBV genome sequences across two regions were shown to be identical in the donor and recipient. The HBV full-length genome sequence from the donor belonged to nonindigenous subgenotype I1. It contained double mutations A1762T and G1764A, which are associated with hepatocellular carcinoma development. The donor had no history of traveling abroad within 126 days prior to the index donation, so he was probably infected with HBV in Japan. DISCUSSION: Including this case, nine cases of TT-HBV from eight blood donations have been detected in Japan since the introduction of ID-NAT. Seven of the eight TT-HBV-related donations had HBV subgenotypes that were exotic to Japan. Exotic HBV strains spreading in Japan pose a risk of TT-HBV owing to ongoing acute HBV infection with these strains.