A virus in the genus Orthopoxvirus (family Poxviridae) which causes smallpox, an acute, highly infectious disease that has been all but eradicated by worldwide vaccination programs. Smallpox, which killed millions of people in epidemics through the ages, causes vomiting, chills, fever, and skin eruptions that often cause permanent scars (pocks).

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.