Hepatitis E virus in donor plasma collected in Japan.

BACKGROUND AND OBJECTIVES: Human hepatitis E virus (HEV) is prevalent worldwide. Iatrogenic HEV has recently been identified based on the reports of transfusion-transmitted cases. The detection rate of HEV-RNA and seroprevalence of HEV-IgG/IgM have been regionally evaluated in Japan, and donor plasma collected in Hokkaido is currently screened by nucleic acid amplification testing. However, the detection rate of HEV-RNA in blood donors in Japan outside of Hokkaido has not been reported.

MATERIALS AND METHODS: A total of 620 140 qualified donor plasma samples from Japanese regions excluding Hokkaido were tested for HEV-RNA (pools of 50 or 500) between 2004 and 2014. HEV-RNA-positive plasma bags were identified, and the HEV viral load, genotype and anti-HEV immunoglobulin (Ig)G/IgM were evaluated.

RESULTS: The detection rate of HEV-RNA (pools of 50) was 1/15 075 and higher in eastern than in western Japan. All 36 HEV-RNA-positive samples were genotype 3 with viral load ranging from <1·69 to 7·22 log10 copies/ml.

CONCLUSIONS: Our detection rate of HEV-RNA in donor populations in Japan outside Hokkaido (1/15 075 donations) is generally lower than reported in Europe and lower than previously reported for Hokkaido (1/8173 donations). As methods varied, we cannot exclude that these differences are reflective of differing RNA detection limits. In contrast to Hokkaido where genotype 4 has been reported among blood donations, all our positive donations were genotype 3, which is less pathogenic.