Reorganizing the family Parvoviridae : 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, Parvovirinae and Densovirinae , 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 certain Densovirinae genera than to members of the Parvovirinae . Viruses belonging to these genera, namely Brevi -, Hepan - and Penstyldensovirus , are responsible for the unmatched heterogeneity of the subfamily Densovirinae when compared to the Parvovirinae in matters of genome organization, protein sequence homology, and phylogeny. Another genus of Densovirinae , 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 genus Ambidensovirus , and introduces new genera and species into the subfamily Parvovirinae . These proposals were accepted by the ICTV in 2020 March.