Orthornavirae

Orthornavirae is a kingdom of viruses that have genomes made of ribonucleic acid (RNA), including genes which encode an RNA-dependent RNA polymerase (RdRp). The RdRp is used to transcribe the viral RNA genome into messenger RNA and to replicate the genome. Viruses in Orthornavirae belong to the realm Riboviria and descend from a common ancestor. The kingdom is subdivided into seven phyla that separate member viruses by genome type, host range and genetic similarity, and it includes positive-strand, negative-strand and double-stranded RNA viruses. Most eukaryotic viruses, including most human, animal and plant viruses, are RdRp-encoding RNA viruses, among them the first virus ever discovered, tobacco mosaic virus.