Notes on Family: Circoviridae



General Description

This family consists of viruses that infect vertebrates and which have circular single-stranded monopartite DNA genomes of <2.5kb. The ORFs are encoded either exclusively in the positive sense or in both directions (ambisense). Some similar vertebrate viruses with larger circular monpartite ssDNA genomes are classified in the genus Anellovirus.


Virions isometric (icosahedral), not enveloped, 12-27 nm in diameter.


Monopartite circular single-stranded DNA of 1.7-2.3 kb. The nonanucleotide sequence TAGTATTAC occurs at the apex of a stem loop and is similar to that of plant viruses in the families Nanoviridae and Geminiviridae.

Genera in the Family

  • Circovirus: ambisense genome smaller than 2.2kb
  • Gyrovirus: positive sense genome larger than 2.2 kb