''Circoviridae'' is a family of DNA viruses. Birds and mammals serve as natural hosts. The family has two genera. Diseases associated with this family include: PCV-2:

postweaning multisystemic wasting syndrome Porcine circoviral disease (PCVD), also known as porcine circovirus associated disease (PCVAD), is a disease seen in domestic pigs. This disease causes illness in Piglet (animal), piglets, with clinical signs including progressive loss of body co ...

; CAV: chicken infectious anemia.

Structure

Viruses in the family ''Circoviridae'' are non-enveloped, with icosahedral and round geometries, and T=1 symmetry. The diameter is around 20 nm. Genomes are circular and non-segmented, around 3.8kb in length. The

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or m ...

consists of 12 pentagonal trumpet-shaped pentamers. There are two main open reading frames arranged in opposite directions that encode the replication and capsid

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

Life cycle

Viral replication is nuclear. Entry into the host cell is achieved by penetration into the host cell. Replication follows the ssDNA rolling circle model. DNA templated transcription, with some alternative splicing mechanism is the method of transcription. The virus exits the host cell by nuclear egress, and nuclear pore export. A stem loop structure with a conserved nonanucleotide motif is located at the 5' intergenic region of circovirus genomes and is thought to initiate rolling-cycle replication. Birds and mammals serve as the natural host. Transmission routes are fecal-oral.

Taxonomy

The family ''Circoviridae'' contains two genera—''

Circovirus ''Circovirus'' is a genus of viruses, in the family ''Circoviridae''. Birds (such as pigeons and ducks) and pigs serve as natural hosts, though dogs have been shown to be infected as well. Circoviruses are single stranded DNA (ssDNA) viruses. The ...

'' and '' Cyclovirus''.

Clinical

A cyclovirus— cyclovirus-Vietnam—has been isolated from the cerebrospinal fluid of 25 Vietnamese patients with CNS infections of unknown aetiology. The same virus has been isolated from the faeces of healthy children and also from pigs and chickens. This suggests an orofaecal route of transmission with a possible animal reservoir.

References

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