Non-enveloped, isometric (icosahedral) but slightly flattened, of three types but similar in size (33 nm). Three RNA components, 2 genomic and 1 subgenomic (sgRNA) are distributed among the particles which can therefore be separated on their densities.
Segmented, tripartite, linear ssRNA(+) genome composed of RNA1=5.4 kb, RNA2=2.2 kb and sgRNA3=1 kb. The 3'-terminal regions of the RNAs may form a stem loop structure, and is not polyadenylated.
The virion RNA is infectious and serves as both the genome and viral messenger RNA. RNA1 has a single open reading frame, RNA2 has two open reading frames and RNA3 is the encapsidated subgenomic of RNA2 expressing the capsid protein.
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNA is translated to produce the proteins necessary for RNA synthesis (replication and transcription).
- Replication takes place in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Expression of the subgenomic RNA (sgRNA3).
- Virus assembly, each segment is encapsidated.
- Virus release.