Tatsunori Nakano

A case of subclinical hepatitis E virus (HEV) infection was detected by nucleic acid amplification test on blood donation. The patient was followed-up until day 220 after the blood donation but showed no symptoms throughout the observation period. Aspartate aminotransferase and alanine aminotransferase levels reached the maximum values on day 37 with a slight increase but remained in normal ranges from day 67 to 220. The quantity of HEV RNA at the initial examination on day 13 was 1.1 × 102 copies/mL, which increased to 2.8 × 103 copies/mL by day 37. It was not detected from day 67 to 220. Immunoglobulin G class antibody to HEV (anti-HEV IgG) was below the cut-off value until day 37 and exceeded the cut-off value to positive on day 67, accompanied by normalization of liver function and negative conversion of HEV RNA. Thereafter, the titer decreased gradually, falling below the cut-off value on day 163, and continuing negative until day 220. Although the persistent duration of anti-HEV IgG positive is believed to be generally long, it was within only 126 days for this subclinical case. Further investigation is needed to determine whether short-term positivity for anti-HEV IgG is typical in subclinical HEV infection.

岐阜県近郊で発生したE型肝炎13例のE型肝炎ウイルス(HEV)の感染源・感染経路を、問診と原因HEVの遺伝子配列の解析から推測した。全員孤発例であった。2例は生のブタ内臓肉、1例は調理したブタ内臓肉、7例は調理したブタ肉、2例は調理不十分なブタ肉の喫食歴があった。HEVゲノムのORF2領域の412塩基長の配列をもとに近隣結合法で系統樹を作成した。1例はORF1領域を解析した。原因HEVの遺伝子型は、3aが5例、3bが6例、3fが1例、4iが1例であった。13例中2例は原因HEV株に近縁株の登録はなかったが、11例には97%以上の相同性を持つ株が見つかり、地域内拡散8例、国内広域拡散2例、国際拡散1例の3つのパターンに類別された。