A number have been isolated from the New World but their association with their host viruses is still being studied.

The genome is between 1300 and 1400 nucleotides in length and has three conserved features: a hairpin structure, a single open reading frame (ORF) and an adenine rich region.

[5] The hairpin structure has a loop that includes the nonanucleotide, TAGTATTAC, which is common to nanoviruses and differs from the TAATATTAC sequence of geminiviruses by one nucleotide.

[6] The open reading frame encodes a rolling circle replication initiator protein (Rep) similar to that found in the nanoviruses.

[9] There are no distinctive virions because the viral genomes are encapsidated within the coat protein of the helper virus.

These tend to be slightly shorter (1100–1300 nucleotides) but to encode proteins in addition to the rep gene.