Picornavirales

**Definition:** Viruses with a monopartitite or bipartite positive-strand RNA genome that share the following properties: auto-proteolytically processed polyprotein(s), a common three-domain replication block (Hel-Pro-Pol domain consisting of a superfamily III helicase, a proteinase with a chymotrypsin-like structure and a superfamily I RNA-dependent RNA polymerase) and non-enveloped icosahedral virions approximately 30 nm in diameter with a pseudo-T=3 symmetry.

**Tree numbers:** - B04.820.578.688