papovavirus is a member of the Papovaviridae family of viruses. Papovaviridae includes two genera: papillomavirus and
The name derives from three abbreviations: Pa for papillomavirus, Po for polyomavirus, and Va for "vacuolating" (simian
vacuolating virus 40 or SV40, which is now known to be part of the polyomavirus genus).
Papovaviruses are DNA viruses containing double-stranded DNA, are icosahedral in shape, and do not have a
They are commonly found in humans and other species, mostly mammals. The one that most often causes disease in
humans is the human papillomavirus.
Note: this family is not used any more in recent taxonomy; each genus has been attributed to its own family,
respectively, Polyomaviridae and Papillomaviridae.
Polyomavirus is the sole genus of viruses within the family Polyomaviridae. Polyomaviruses are DNA-based
(double-stranded DNA,~5000 base pairs,circular genome), 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
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
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.
Papillomaviruses were first identified in the early 20th century, when it was shown that skin warts, or papillomas, could
be transmitted between individuals by a filterable infectious agent. In 1935 Francis Peyton Rous, who had previously
demonstrated the existence of a cancer-causing sarcoma virus in chickens, went on to show that a papillomavirus could
cause skin cancer in infected rabbits. This was the first demonstration that a virus could cause cancer in mammals.
It is now recognized that papillomaviruses are a diverse group of non-enveloped DNA viruses that infect animals ranging
from birds to manatees (Moreno-Lopez 1984) (Rector 2004). More than 100 different human papillomavirus (HPV) types
have also been identified. As with rabbit papillomaviruses, some HPV types can cause cancer, most notably cervical
cancer. Clinical aspects of HPV infection are outlined in the main article human papillomavirus. The current article
addresses the biology of papillomaviruses in general.