2024 taxonomy update for the family Circoviridae

Abstract

Circovirids have a circular single-stranded DNA genome packed into a small icosahedral capsid. They are classified within two genera, Circovirus and Cyclovirus, in the family Circoviridae (phylum Cressdnaviricota, class Arfiviricetes, order Cirlivirales). Over the last five years, a number of new circovirids have been identified, and, as a result, 54 new species have been created for their classification based on the previously established species demarcation criterion, namely, that viruses classified into different species share less than 80% genome-wide pairwise sequence identity. Of note, one of the newly created species includes a circovirus that was identified in human hepatocytes and suspected of causing liver damage. Furthermore, to comply with binomial species nomenclature, all new and previously recognized species have been (re)named in binomial format with a freeform epithet. Here, we provide a summary of the properties of circovirid genomes and their classification as of June 2024 (65 species in the genus Circovirus and 90 species in the genus Cyclovirus). Finally, we provide reference datasets of the nucleotide and amino acid sequences representing each of the officially recognized circovirid species to facilitate further classification of newly discovered members of the Circoviridae.