Reorganizing the familyParvoviridae: a revised taxonomy independent of the canonical approach based on host association

Parvoviridae, a diverse family of small single-stranded DNA viruses was established in 1975. It was divided into two subfamilies,ParvovirinaeandDensovirinae, in 1993 to accommodate parvoviruses that infect vertebrate and invertebrate animals, respectively. This relatively straightforward segregation, using host association as the prime criterion for subfamily-level classification, has recently been challenged by the discovery of divergent, vertebrate-infecting parvoviruses, dubbed chapparvoviruses, which have proven to be more closely related to viruses in certainDensovirinaegenera than to members of theParvovirinae. Viruses belonging to these genera, namelyBrevi-,Hepan- andPenstyldensovirus, are responsible for the unmatched heterogeneity of the subfamilyDensovirinaewhen compared to theParvovirinaein matters of genome organization, protein sequence homology, and phylogeny. Another genus ofDensovirinae,Ambidensovirus, has challenged traditional parvovirus classification, as it includes all newly discovered densoviruses with an ambisense genome organization, which introduces genus-level paraphyly. Lastly, current taxon definition and virus inclusion criteria have significantly limited the classification of certain long-discovered parvoviruses and impedes the classification of some potential family members discovered using high-throughput sequencing methods. Here, we present a new and updated system for parvovirus classification, which includes the introduction of a third subfamily,Hamaparvovirinae, resolves the paraphyly within genusAmbidensovirus, and introduces new genera and species into the subfamilyParvovirinae. These proposals were accepted by the ICTV in 2020 March.