title: What is a virus?
abstract: The earlier reluctance of some plant virologists to use the term "virus species" has been overcome and the species has now been accepted as the basic unit in virus classification. A virus species is a polythetic class of viruses that constitutes a replicating lineage and occupies a particular ecological niche. Because of the polythetic nature of virus species, there is no single property, such as a particular level of genome homology, that could be used as the sole criterion for delineating individual virus species.
authors.affiliation: Institut de Biologie Moleculaire et Cellulaire, Strasbourg, France.
authors.forename: M H
authors.initials: MH
authors.lastname: Van Regenmortel
mesh_terms: D010942:Plant Viruses / Q000145:classification; D013045:Species Specificity; D014780:Viruses / Q000145:classification*