text: There are 4 superfamilies of viruses that cover all RNA-containing viruses with no DNA stage:
  * Viruses containing positive-strand RNA or double-strand RNA, except retroviruses and Birnaviridae
  ** All positive-strand RNA eukaryotic viruses with no DNA stage
  ** All RNA-containing bacteriophages; there are two families of RNA-containing bacteriophages: Leviviridae (positive ssRNA phages) and Cystoviridae (dsRNA phages)
  ** dsRNA virus family Reoviridae, Totiviridae, Hypoviridae, Partitiviridae
  * Mononegavirales (negative-strand RNA viruses with non-segmented genomes; )
  * Negative-strand RNA viruses with segmented genomes (), such as orthomyxoviruses and bunyaviruses
  * dsRNA virus family Birnaviridae ()
  Flaviviruses produce a polyprotein from the ssRNA genome. The polyprotein is cleaved to a number of products, one of which is NS5, an RNA-dependent RNA polymerase. This RNA-directed RNA polymerase possesses a number of short regions and motifs homologous to other RNA-directed RNA polymerases.
  RNA replicase found in positive-strand ssRNA viruses are related to each other, forming three large superfamilies. Birnaviral RNA replicase is unique in that it lacks motif C (GDD) in the palm. Mononegaviral RdRp (PDB 5A22) has been automatically classified as similar to (+)−ssRNA  RdRps, specifically one from Pestivirus and one from Leviviridae. Bunyaviral RdRp monomer (PDB 5AMQ) resembles the heterotrimeric complex of Orthomyxoviral (Influenza; PDB 4WSB)  RdRp.
  Since it is a protein universal to RNA-containing viruses, RdRp is a useful marker for understanding their evolution. The overall structural evolution of viral RdRps has been reviewed.