A phylogenetic tree based on the complete genomic sequences of 30 human, swine, and avian HEV strains. Genotypes 1 and 2 HEV are restricted to humans, whereas genotypes 3 and 4 HEV infect both humans and swine. The avian HEV likely belongs to a separate genus within the family. A scale bar, indicating the number of character state changes, is proportional to the genetic distance.