Enveloped, spherical, about 50 nm in diameter.


Monopartite, linear, ssRNA(+) genome of about 10 kb. There is an internal ribosome entry site (IRES) at the 5' end that mediates translation initiation. The genome does not appear to encode a capsid (or core) protein. The virions, however, have a nucleocapsid. It is not clear if an additional capsid protein might arise from cleavage of the N-terminus or from an alternative reading frame.


The virion RNA is infectious and serves as both the genome and the viral messenger RNA. The whole genome is translated in a polyprotein, which is processed co- and post-translationally by host and viral proteases.


  1. Attachement of the viral envelope protein E to host receptors mediates internalization into the host cell by clathrin-mediated endocytosis.
  2. Fusion of virus membrane with host endosomal membrane. RNA genome is released into the cytoplasm.
  3. The positive-sense genomic ssRNA is translated into a polyprotein, which is cleaved into all structural and non structural proteins (to yield the replication proteins).
  4. Replication takes place at the surface of endoplasmic reticulum in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+). Host miRNA mir-122 plays a essential role in initiating replication.
  5. The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
  6. Virus assembly occurs at the endoplasmic reticulum. The virion probably buds at the endoplasmic reticulum, is transported to the Golgi apparatus.
  7. Release of new virions by exocytosis.