Hepatitis B virus
The Avian HBV RNA encapsidation signal epsilon (AHBV epsilon) is an RNA structure that is shown to facilitate encapsidation of the pregenomic RNA required for viral replication. There are two main classes of encapsidation signals in avian hepatitis B viruses - "Duck hepatitis B virus" (DHBV) and "Heron hepatitis B virus" (HHBV) like. DHBV is used as a model to understand human "Hepatitis B virus". Although studies have shown that the HHBV epsilon has less pairing in the upper stem than DHBV, this pairing is not absolutely required for DHBV infection in ducks.