E型肝炎的新觀念

Current Concepts of Hepatitis E

E型肝炎病毒是一種小型、非包膜病毒，直徑約27～34 nm，該病毒有一個單鏈RNA，約7.2 kb的長度。E型肝炎病毒的基因結構是相當獨特的，歸類於Hepeviridae科Hepevirus屬。依基因組的序列分析，人和豬E型肝炎病毒分為四個基因型，即基因型1，2，3和4型。基因型1和2型被確定會引起流行性肝炎，由污染的水和糞口傳染人類。基因型3和4型在家豬和野豬是常見的，人類室意外宿主。E型肝炎病毒感染的臨床症狀是多樣的。它最常見的表現為自限性或急性黃疸型肝炎。當懷孕時感染E型肝炎病毒，疾病嚴重的風險增加。免疫功能低下者，包括使用免疫抑制藥物的器官移植接受者，癌症接受化療的病人和愛滋病病毒感染者的慢性E型肝炎病毒感染已被確定，有些病人會有進行性肝纖維化或肝硬化。在中國生產的重組E型肝炎疫苗，在對照試驗中，有超過95%的保護效果。因此E型肝炎預防可由施打E型肝炎疫苗實現。

Hepatitis E virus (HEV) is a small, non-enveloped virus, approximately 27-34 nm in diameter. The virus has a single-stranded RNA genome, approximately 7.2 kilobases in length. The genomic structure of HEV is unique, defining its position in the genus Hepevirus of the Hepeviridae family. On genomic sequence analysis, human and swine HEV isolates fall into 4 genotypes, namely genotypes 1, 2, 3, and Genotypes 1 and 2 are human viruses that have been shown to cause epidemic hepatitis via waterborne and fecal-oral transmission. Genotypes 3 and 4 are swine viruses that are common in domestic and wild pigs and appear to infect humans as an accidental host. The clinical outcomes associated with HEV infection are quite diverse. It most commonly manifests as a self-limiting or acute icteric hepatitis. HEV infection in pregnancy is associated with increased risk of severe disease. Chronic infection has been identified exclusively among immunocompromised persons, including organ-transplant recipients, patients receiving cancer chemotherapy, and HIV-infected persons. Some patients progress to liver disease with fibrosis or cirrhosis. A recombinant HEV vaccine produced in China was shown to have more than 95% efficacy in a controlled trial. Therefore, prevention of hepatitis E is achievable through vaccination.