Non-enveloped, spherical, capsid of about 27-33 nm with icosahedral symmetry. The virion is constructed from two capsid proteins VP1 and VP2.


Monopartite, linear, ssRNA(+) genome of 10-11 kb in size, polyadenylated.


The virion RNA is infectious and serves as both the genome and viral messenger RNA.



  1. Attachement to host receptors mediates entry into the host cell.
  2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
  3. Viral RNA is translated in a polyprotein to produce replication proteins.
  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. Subgenomic RNA translation gives rise to the capsid proteins.
  7. Assembly of new virus particles.
  8. Virus release.