Virus classes

thumb|upright=1.8| (A) When the host cell is only infected by a giant virus, the latter establishes a cytoplasmic virus factory to replicate and generates new virions, and the host cell is most likely [[lysed at the end of its replication cycle.(B) When the host cell is co-infected with a giant virus and its virophage, the latter parasitizes the giant virus's virus factory. The presence of virophages could seriously impact the infectivity of the giant virus by decreasing its replication efficiency and increasing the survival of the host cell.(C) When the giant virus genome is parasitized by a

Revtraviricetes is a class of viruses that contains all viruses that encode a reverse transcriptase. The group includes all ssRNA-RT viruses (including the retroviruses) and dsDNA-RT viruses. It is the sole class in the phylum Artverviricota, which is the sole phylum in the kingdom Pararnavirae. The name of the group is a portmanteau of "reverse transcriptase" and -viricetes which is the suffix for a virus class.

Monjiviricetes is a class of negative-strand RNA viruses which infect fungi, plants, invertebrates, and vertebrates. The name is a portmanteau of the two orders within the class, Mononegavirales and Jingchuvirales and the suffix for a virus class -viricetes.

Megaviricetes is a class of viruses. The class contains giant viruses, all of which are nucleocytoplasmic large DNA viruses that are assigned to the phylum Nucleocytoviricota. Members of the Megaviricetes typically have genomes that are much larger than viruses assigned to other taxa, and also encode genes involved in DNA repair, DNA replication, transcription, translation, and other processes that viruses in other taxa usually lack. As well, the virus particles (virions) of some members of Megaviricetes are much larger in size than for other viruses, and can be larger than some bacteria.

Alsuviricetes is a class of positive-strand RNA viruses which infect eukaryotes. The name of the group is a syllabic abbreviation of "alpha supergroup" with the suffix -viricetes indicating a virus class.

Pisoniviricetes is a class of positive-strand RNA viruses which infect eukaryotes. A characteristic of the group is a conserved 3C-like protease from the PA clan of proteases for processing the translated polyprotein. The name of the group is a portmanteau of member orders "picornavirales, sobelivirales, nidovirales" and -viricetes which is the suffix for a virus class.

Papovaviricetes is a class of viruses. The class shares the name of an abolished family, Papovaviridae, which was split in 1999 into the two families Papillomaviridae and Polyomaviridae. The class was established in 2019 and takes its name from the former family.

thumb|Tailed bacteriophage structure: (1) head, (2) tail, (3) DNA, (4) capsid, (5) collar, (6) sheath, (7) tail fibres, (8) spikes, (9) base plate thumb|Transmission electron microscopy|Transmission electron micrograph of Gamma-Phage thumb|right|Illustrations of various caudoviricetes. Not to scale.