Notes on Family: Picobirnaviridae



General Description

This family was created to accommodate animal virus species that were previously classified in the family Birnaviridae because of their bipartite dsRNA genomes. However, the picobirnaviruses have smaller particles and smaller genome segments than the birnaviruses. There are no sequence similarities between the two groups and the picobirnaviruses have a different type of RNA polymerase. Picobirnaviruses infect mammals, whereas the only known vertebrate hosts of birnaviruses are fish and birds. The name is derived from the Spanish pico (=small) with birna for bipartite RNA.


Virions isometric (icosahedral), not enveloped, 35-40 nm in diameter.


Bipartite double-stranded RNA totalling 4-4.5 kb. The coat protein is encoded by the second ORF of the larger segment and the polymerase by the only ORF on the smaller segment.

Genera in the Family

There is currently only one genus: