Poxviruses

The name of the family, Poxviridae, is a legacy of the original grouping of viruses associated with diseases that
produced poxs in the skin. Modern viral classification is based on the shape and molecular features of viruses, and the
smallpox virus remains as the most notable member of the family. The only other poxvirus known to specifically infect
humans is the molluscum contagiosum virus (MCV).3

Molluscum contagiosum (MC) is a viral infection of the skin or occasionally of the mucous membranes. MC infects
humans, other primates and kangaroos. The infecting virus is a DNA poxvirus called the molluscum contagiosum virus
(MCV). There are 4 types of MCV, MCV-1 to -4, with MCV-1 being the most prevalent and MCV-2 seen usually in adults
and often sexually transmitted. The incidence of MC infections in young children is around 17% and peaks between
2-12 years of age. MC affects any area of the skin but is most common on the body, arms, and legs. It is spread
through direct contact, saliva, or shared articles of clothing (including towels).

In adults, molluscum infections are often sexually transmitted and usually affects the genitals, lower abdomen, buttocks,
and inner thighs. In rare cases, molluscum infections are also found on the lips and mouth.

(members of the family Poxviridae) can infect as a family both vertebrate and invertebrate animals. Poxviridae viral
particles (virions) are generally enveloped (external enveloped virion- EEV), though the internal mature virion (IMV)
form of the virus, which contains different envelope, is also infectious. They vary in their shape depending upon the
species but are generally shaped like a brick or as an oval form similar to a rounded brick. The virion size is around 200
nm in diameter and 300 nm in length and carries its genome in a single, circular, double-stranded segment of DNA 1.
By comparison, Rhinovirus is 1/10th as large as a typical Poxviridae virion2. Electron micrographs of Orthopoxvirus and
Parapoxvirus Genera, including the smallpox virus, have been collected by the International Committee on Taxonomy of
Viruses in their Poxviridae picture gallery. The prototype of poxvirus family is vaccinia virus, which has been used as a
successful vaccine to eradicate smallpox virus. Vaccinia virus is also used as an effective tool for foreign protein
expression to elicite strong host immune response. Vaccinia virus enters cells mainly by cell fusion, although currently
the receptor is not known. Virus contains three classes of genes, early, intermediate and late, that are transcribed by
viral RNA polymerase and associated transcription factors. Vaccinia virus replicates its genome in cytoplasm of the
infected cells and after late gene expression virion morphogenesis produces IMV that contains envelope, although the
origin of the envelope membrane is still unknown. IMV is transported to Golgi to be wrapped additional two membrane to
become intracellular enveloped virus (IEV). IEV transports along microtubules to reach cell periphery and fuse with
plasma membrane to become cell-associated enveloped virus (CEV) that triggers actin tails on cell surfaces or is
releared as EEV.


The following genera are currently included here:
Subfamily Chordopoxvirinae
Genus Orthopoxvirus; type species: Vaccinia virus; diseases: cowpox, vaccinia, smallpox
Genus Parapoxvirus; type species: Orf virus
Genus Avipoxvirus; type species: Fowlpox virus
Genus Capripoxvirus; type species: Sheeppox virus
Genus Leporipoxvirus; type species: Myxoma virus
Genus Suipoxvirus; type species: Swinepox virus
Genus Molluscipoxvirus; type species: Molluscum contagiosum virus
Genus Yatapoxvirus; type species: Yaba monkey tumor virus
Subfamily Entomopoxvirinae
Genus Entomopoxvirus A; type species: Melolontha melolontha entomopoxvirus
Genus Entomopoxvirus B; type species: Amsacta moorei entomopoxvirus
Genus Entomopoxvirus C; type species: Chironomus luridus entomopoxvirus

http://encyclopedia.thefreedictionary.com/poxviruses