Non-enveloped, about 30 nm in diameter, T=pseudo3 icosahedral capsid. Genome segments are encapsidated separately into two different types of particle similar in size.



Segmented, bipartite linear ssRNA(+) genome composed of RNA.1=7.8 kb and RNA-2=5.4 kb. Each genomic segment has a VPg linked to its 5' end and a 3' poly(A) tract.


The virion RNA is infectious and serves as both genome and mRNA.
RNA-1 and RNA-2 are translated into two polyproteins, which are then processed into functional proteins. RNA-1 encodes proteins necessary for replication, while RNA-2 encodes one or two capsid proteins and product(s) involved in cell-to-cell movement.



  1. Virus penetrates into the cell.
  2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
  3. Synthesis and proteolytic cleavage of the replicase polyprotein RNA-1.
  4. Replication occurs in viral factories made of membrane vesicles derived from the ER. A dsRNA genome is synthesized from the genomic ssRNA(+).
  5. The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
  6. Assembly of new virus particles.
  7. Movement protein allows cell-to-cell movement.