Birnaviridae: A family of bisegmented, double-stranded RNA viruses causing infection in fish, mollusks, fowl, and Drosophila. There are three genera: AQUABIRNAVIRUS; AVIBIRNAVIRUS; and ENTOMOBIRNAVIRUS. Horizontal and vertical transmission occurs for all viruses.Aquabirnavirus: A genus of RNA viruses in the family BIRNAVIRIDAE infecting fish, mollusks, and crustaceans. It is transmitted both vertically and horizontally with no known vectors. The natural hosts are salmonids and the type species is INFECTIOUS PANCREATIC NECROSIS VIRUS.Birnaviridae Infections: Virus diseases caused by the BIRNAVIRIDAE.Infectious bursal disease virus: A species of AVIBIRNAVIRUS causing severe inflammation of the bursa of Fabricius in chickens and other fowl. Transmission is thought to be through contaminated feed or water. Vaccines have been used with varying degrees of success.Infectious pancreatic necrosis virus: The type species of AQUABIRNAVIRUS, causing infectious pancreatic necrosis in salmonid fish and other freshwater and marine animals including mollusks.Viral Structural Proteins: Viral proteins that are components of the mature assembled VIRUS PARTICLES. They may include nucleocapsid core proteins (gag proteins), enzymes packaged within the virus particle (pol proteins), and membrane components (env proteins). These do not include the proteins encoded in the VIRAL GENOME that are produced in infected cells but which are not packaged in the mature virus particle,i.e. the so called non-structural proteins (VIRAL NONSTRUCTURAL PROTEINS).Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.