An RNA virus is a virus characterized by a ribonucleic acid (RNA) based genome. The genome can be single-stranded RNA (ssRNA) or double-stranded (dsRNA). Notable human diseases caused by RNA viruses include influenza, SARS, MERS, COVID-19, Dengue virus, hepatitis C, hepatitis E, West Nile fever, Ebola virus disease, rabies, polio, mumps, and measles.
All RNA viruses use a homologous RNA-dependent polymerase for replication and are categorized by the International Committee on Taxonomy of Viruses (ICTV) into the realm Riboviria. This includes viruses belonging to Group III, Group IV, Group V, and Group VI of the Baltimore classification system. Group VI comprises the retroviruses, which have RNA genetic material but use DNA intermediates in their life cycle. Riboviria does not include viroids and satellite nucleic acids: Deltavirus, Avsunviroidae, and Pospiviroidae are taxa that were mistakenly included in 2019, but this was corrected in 2020.