Duck virus hepatitis (DVH) is typically associated with an acute, contagious infection in susceptible ducklings less than 6 weeks of age and frequently under 3 weeks of age. It does not occur in older birds. The disease, DVH, has traditionally been subdivided into types I, II and III. DVH type I can be caused by at least three different genotypes of duck hepatitis A virus (DHAV) virus, a member of the genus Avihepatovirus, of the family Picornaviridae. The most pathogenic and widespread is DHAV type 1 (DHAV-1). DHAV-2 and DHAV-3 are two additional genotypes within the genus Avihepatovirus that have subsequently been identified as additional aetiological agents of DVH in ducklings. DVH type II is caused by duck astrovirus type 1 (DAstV-1), a member of the Astroviridae family. It has been reported in ducklings from 10 days to 6 weeks of age, and causes pathological changes similar to those of DHAV-1. DVH type III is caused by duck astrovirus type 2 (DAstV-2), a member of the Astroviridae. It is considered distinct from DAstV-1 and has been reported only in the United States of America. It causes similar liver lesions in young ducklings, but is less virulent than DHAV. DHAV-1 infections can be controlled by the use of live attenuated virus vaccines and an inactivated virus vaccine. DAstV-2 infections can be controlled by the use of a live attenuated virus vaccine given to breeder ducks to confer passive immunity to ducklings. The causal viruses of DVH are not considered zoonotic.