Hepatitis E Virus.

Since the sequence of hepatitis E virus (HEV) was determined from a patient with enterically transmitted non-A, non-B hepatitis in 1989, similar sequences have been isolated from many different animals, including pigs, wild boars, deer, rabbits, bats, rats, chicken, and trout. All of these sequences have the same genomic organization, which contains open reading frames (ORFs) 1, 2, and 3, although their genomic sequences are variable. Some have proposed that they be classified as new family, Hepeviridae, which would be further divided into different genera and species according to their sequence variability. The size of these virus particles generally ranged from 27 to 34 nm. However, HEV virions produced in cell culture differ in structure from the viruses found in feces. Those from cell culture have a lipid envelope and either lack or have a little ORF3, whereas the viruses isolated from feces lack a lipid envelope but have ORF3 on their surfaces. Surprisingly, most of the secreted ORF2 proteins from both these sources are not associated with HEV RNA.