Non-enveloped, isometric, icosahedral, about 30 nm in diameter.



Linear, C-rich, ssRNA(+) genome of 7.5 kb. The 3' terminus has a poly(A) tract.


The virion RNA is infectious and serves as both the genome and viral messenger RNA. The genomic RNA encodes a large replication polyprotein which is cleaved. The capsid protein and two small proteins are translated from two or more 3'-coterminal subgenomic RNAs.


  1. Virus penetrates into the host cell.
  2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
  3. The viral RNA is translated to produce the protein necessary for RNA synthesis (replication and transcription).
  4. Replication occurs in viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
  5. The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
  6. The RdRp recognizes an internal subgenomic promoter on the negative-sense RNA to transcribe the 3'co-terminal subgenomic RNA that will generate the capsid protein.
  7. Assembly of new virus particles.