Hepatitis E virus (HEV): molecular biology and emerging epidemiology

The etiologic agent of what was formerly known as enterically transmitted non-A, non-B hepatitis has been identified as a previously unrecognized 27 to 34 nm nonenveloped virus designated as HEV. The full-length sequencing of four geographic isolates has demonstrated HEV to be a positive-sense, polyadenylated RNA virus expressed in three different ORFs. The identification and localization of (1) sequence motifs characteristic of viral nonstructural genes, (2) signal peptides and basic sequences characteristic of structural (capsid) genes, and (3) immunodominant antigens has established that the genomic organization and expression strategy of HEV is unlike that of other characterized positive-sense RNA viruses.