Smallpox is caused by infection with variola virus, which belongs to the
genus Orthopoxvirus, the family Poxviridae and subfamily chordopoxvirinae.
Variola is a large brick-shaped virus measuring approximately 302 to 350 nanometers
by 244 to 270 nm, with a single linear double stranded DNA genome 186 kilobase
pairs (kbp) in size and containing a hairpin loop at each end. The two classic
varieties of smallpox are variola major and variola minor.
genus Orthopoxvirus, the family Poxviridae and subfamily chordopoxvirinae.
Variola is a large brick-shaped virus measuring approximately 302 to 350 nanometers
by 244 to 270 nm, with a single linear double stranded DNA genome 186 kilobase
pairs (kbp) in size and containing a hairpin loop at each end. The two classic
varieties of smallpox are variola major and variola minor.
Four orthopoxviruses cause infection in humans: variola, vaccinia, cowpox,
and monkeypox. Variola virus infects only humans in nature, although primates
and other animals have been infected in a laboratory setting. Vaccinia, cowpox,
and monkeypox viruses can infect both humans and other animals in nature.
and monkeypox. Variola virus infects only humans in nature, although primates
and other animals have been infected in a laboratory setting. Vaccinia, cowpox,
and monkeypox viruses can infect both humans and other animals in nature.
The lifecycle of poxviruses is complicated by having multiple infectious
forms, with differing mechanisms of cell entry. Poxviruses are unique among DNA
viruses in that they replicate in the cytoplasm of the cell rather than in the nucleus.
In order to replicate, poxviruses produce a variety of specialized proteins not
produced by other DNA viruses, the most important of which is a
viral-associated DNA-dependent RNA polymerase.
forms, with differing mechanisms of cell entry. Poxviruses are unique among DNA
viruses in that they replicate in the cytoplasm of the cell rather than in the nucleus.
In order to replicate, poxviruses produce a variety of specialized proteins not
produced by other DNA viruses, the most important of which is a
viral-associated DNA-dependent RNA polymerase.
Both enveloped and unenveloped virions are infectious. The viral
envelope is made of modified Golgi membranes containing viral-specific
polypeptides, including hemagglutinin. Infection with either variola major or
variola minor confers immunity against the other.
envelope is made of modified Golgi membranes containing viral-specific
polypeptides, including hemagglutinin. Infection with either variola major or
variola minor confers immunity against the other.
