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Baltimore Classification

Higher order taxa

Viruses; dsRNA viruses; Birnaviridae


Aquabirnavirus, Avibirnavirus, Entomobirnavirus

Description and Significance

Birnaviruses infect animals: vertebrates, insects, molluscs and crustaceans. They are bi-RNA viruses and have double stranded RNA genomes in two components.

Genome Structure

The genome of Binyaviridae is segmented and consists of linear double-stranded RNA. Minor species of non-genomic nucleic acid are also found in virions. The complete genome is 5880-6400 nucleotides long. Segment A has been fully sequenced and the complete sequence is 3100-3200 nucleotides long while segment B is 2750-2850 nucleotides long. The genome guanine+cytosine content is 45.5-54.5 %. The 5'-end of the genome has a cap on both segments genome-linked protein (VPg). The multipartite genome is found in one type of particle only. (source ICTV dB Descriptions)

Virion Structure of a Birnaviridae

The virions of a birnaviridae have a simple construction. The virions are not enveloped and consist of a capsid. The capsid is round and exhibits icosahedral symmetry (T=13). The capsid shells of the virions are composed of a single layer. The capsids appear hexagonal in outline. The capsomer arrangement is clearly visible and there are 132 capsomers in the capsid. There are no surface projections and the capsids all have the same appearance.

Reproduction Cycle of a Birnaviridae in a Host Cell

Viral Ecology & Pathology