Notes on Family: Birnaviridae



General Description

This family consists of viruses that infect animals (vertebrates, insects, molluscs and crustaceans) and which have double stranded RNA genomes in two components (bi-RNA-viruses). The isometric virions (60 nm) are much larger than those in the family Partitiviridae, whose members infect plants or fungi.


Virions isometric (icosahedral), not enveloped, 60 nm in diameter, made of 260 units trimeric subunits.


Bipartite double-stranded RNA totalling 5.8-6.5 kb with a genome-linked protein (VPg) at the 5'-termini. There is no 3'-polyA tail. Each segment encodes a large polyprotein that it is subsequently processed into the functional products and there is an additional, smaller ORF on the larger (A) segment. The capsid proteins are encoded on segment A and an RNA-dependent RNA polymerase on segment B.

Genera in the Family