See text Polyomavirus is the sole genus of viruses within the family Polyomaviridae. Polyomaviruses are DNA-based, small (40-50 nanometers in diameter), and icosahedral in shape, and do not have a lipoprotein envelope. They are potentially oncogenic (tumor-causing); they often persist as latent infections in a host without causing disease, but may produce tumors in a host of a different species, or a host with an ineffective immune system. The name polyoma refers to the viruses' ability to produce multiple (poly-) tumors (-oma).

There are two polyomaviruses found in humans: JC virus, which can infect the respiratory system, kidneys, or brain (sometimes causing the fatal progressive multifocal leukoencephalopathy in the latter case), and BK virus , which produces a mild respiratory infection and can affect the kidneys of immunosuppressed transplant patients. Both viruses are very widespread: approximately 80 percent of the adult population in the United States have antibodies to BK and JC.

The Simian vacuolating virus 40 replicates in the kidneys of monkeys without causing disease, but causes sarcomas in hamsters. It is unknown whether it can cause disease in humans, which has caused concern since the virus may have been introduced into the general population in the 1950s through a contaminated polio vaccine.

An avian polyomavirus sometimes referred to as the Budgerigar fledgling disease virus is a frequent cause of death among caged birds.

The genus Polyomavirus used to be one of two genera within the now obsolete family Papovaviridae (the other genus being Papillomavirus which is now assigned to its own family Papillomaviridae). The name Papovaviridae derives from three abbreviations: Pa for Papillomavirus, Po for Polyomavirus, and Va for "vacuolating".

Species

• African green monkey polyomavirus (AGMPyV)
• Baboon polyomavirus 2 (PPyV)
• BK polyomavirus (BKPyV)
• Bovine polyomavirus (BPyV)
• Budgerigar fledgling disease virus (BFPyV)
• Hamster polyomavirus (HaPyV)
• JC polyomavirus (JCPyV)
• Murine pneumotropic virus (MPtV)
• Murine polyomavirus (MPyV)
• Rabbit kidney vacuolating virus (RKV)
• Simian virus 12 (SV-12)
• Simian virus 40 (SV-40, type species)