Realm (virology)
In virology, realm is the highest taxonomic rank established for viruses by the International Committee on Taxonomy of Viruses (ICTV), which oversees virus taxonomy. Ten virus realms are recognized and united by specific highly conserved traits: Adnaviria, which contains archaeal filamentous viruses with A-form double-stranded (ds) DNA genomes encoding a unique alpha-helical major capsid protein; Duplodnaviria, which contains all dsDNA viruses that encode the HK97-fold major capsid protein; Efunaviria, from the sixth Latin letter “ef” and the Latin una, meaning “one”, referring to Enterobacteria phage f1, which encodes the hallmark morphogenic module of this realm; Floreoviria, which contains all single-stranded DNA (ssDNA) viruses that encode an HUH superfamily endonuclease and their descendants; Pleomoviria, a reference to the pleomorphic morphology of viruses in this realm; Riboviria, which contains all RNA viruses that encode RNA-dependent RNA polymerase and all viruses that encode reverse transcriptase; Ribozyviria, which contains hepatitis delta virus-like viruses with circular, negative-sense ssRNA genomes; Singelaviria, which contains all DNA viruses that have two major capsid proteins (MCPs) that both have a single jelly roll (SJR) fold; Varidnaviria, which contains all dsDNA viruses that encode a vertical jelly roll major capsid protein; Volvereviria, from the Latin volvere, meaning “to roll”, referring to the rolling circle replication uniformly used by viruses in this realm.