Smallpox causes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
Smallpox is caused by the variola virus.
Taxonomy
Viruses; dsDNA; Poxviridae; Chordopoxvirinae; Orthopoxvirus; Variola vera
Biology
Variola virus is a orthopoxvirus, from the family Poxviridae, the largest viruses to infect humans. It is a 200-400 nm dsDNA virus, lacking icosahedral symmetry. The other viruses of the family Poxviridae include the vaccinia, the molluscum contagiosum, the cowpox and the monkeypox. (6) The viral structure includes:
- Outer membrane
- 2 lateral bodies
- 1 dsDNA molecule in its core containing 186,999 base pairs (7), (8), (9)
Variola virus genes are similar to the ones of vaccinia virus, which made possible using the vaccinia virus as a vaccine for smallpox virus. (10)
There are 2 forms of variola virus:
- Variola major
- Variola minor
Both strains of the virus share a large amount of genome, which leads to the assumption that the difference in virulence resides in alternate gene expression,
Origin
Tropism
Natural reservoir
Humans are the only natural reservoir of smallpox virus.[1]