International Committee on Taxonomy of Viruses

The International Committee on Taxonomy of Viruses (ICTV) is the body responsible for naming and classifying viruses. Founded in 1966, it publishes the official taxonomy through expert study groups and an annual update of the virus Master Species List.

Working groups of specialists propose new species, genera and families, which are debated by the committee and then ratified by vote. Because viruses do not share a single common ancestor, the system relies on genome organization, replication strategy and sequence relationships rather than a single tree of life. The ICTV deals only with classification and species names, not with the names of diseases, which are decided separately by the World Health Organization.

The framework has up to fifteen ranks, from realm at the top, through kingdom, phylum, class, order and family, down to genus and species. Since 2019, species names follow a binomial form similar to that in biology, for example a genus name followed by a species epithet. The informal names people use, such as Zika virus or dengue virus, are kept as virus names even when the species name differs.

The Baltimore system, proposed by David Baltimore in 1971, sorts viruses into seven groups by how they produce mRNA, such as DNA viruses, RNA viruses and retroviruses. The ICTV system complements it by organizing viruses by relatedness, and the two are often used together. Examples of families it recognizes include the Flaviviridae.

• Virus — what it classifies
• Flaviviridae — an example family it recognizes
• RNA Virus — a major group in the Baltimore system