Orthopoxvirus

The genus of the family Poxviridae, which comprises the viruses of alastrim, vaccinia, variola, cowpox, ectromelia, monkeypox, and rabbitpox.

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or·tho·pox·vi·rus 'ȯr-thō-päks-.vī-rəs, ȯr-thō-'päks- n

1) cap a genus of poxviruses that are brick-shaped measuring about 200 by 200 by 250 nanometers, that hybridize extensively within the genus and sometimes with the DNA of members of other poxvirus genera, and that include the vaccina virus and the causative agents of cowpox, monkeypox, mousepox, and smallpox

2) any of the genus Orthopoxvirus of poxviruses

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Or·tho·pox·vi·rus (orґtho-poks-vi″rəs) [ortho- + poxvirus] a genus of viruses of the subfamily Chordopoxvirinae (family Poxviridae) with nucleic acid homology and serologic cross-reactivity that cause generalized infections with a rash in mammals, including camelpox, cowpox, ectromelia, monkeypox, and vaccinia viruses. The virtually extinct agent of smallpox, variola virus, belongs to this genus.