Hepatitis A Virus (HAV) is a 27nm nonenveloped, spherical, positive stranded RNA virus, classified within the genus hepatovirus of the picornavirus family and is among the smallest and structurally simplest of the RNA animal viruses. A single large polyprotein is expressed from a large open reading frame extending through most of the genomic RNA. This polyprotein is subsequently cleaved by a viral protease (3Cpro) to form three (possibly four) capsid proteins and several nonstructural proteins. HAV genomic replication occurs exclusively in the cytoplasm of the infected hepatocyte by a mechanism involving an RNA-dependent RNA polymerase.