Non enveloped, icosahedral virion about 35 nm in diameter. Contains three kind of proteins.


Linear segmented genome composed of two RNAs of respectively 6.2 and 5.9 kb.


The dsRNA genome is never completely uncoated, to prevent activation of antiviral state by the cell in response to dsRNA. The viral polymerase synthesizes a mRNA, which is translocated to the cell cytoplasm where it is translated.



  1. Attachement to host receptors mediates entry of the virus into the cell.
  2. Transcription of the dsRNA genome by viral polymerase occurs inside the virion, so that dsRNA is never exposed to the cytoplasm. This plus-strand transcript is used as template for translation.
  3. (+)RNAs are encapsidated in a sub-viral particle, in which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
  4. Mature virions are released.