| − | Smallpox is an acute, highly infectious, often fatal disease caused by a poxvirus and characterized by high fever and aches with subsequent widespread eruption of pimples that blister, produce pus, and form pockmarks. It is also called variola. | + | Smallpox is an acute, highly infectious, often fatal disease caused by a poxvirus and characterized by high fever and aches with subsequent widespread eruption of pimples that blister, produce pus, and form pockmarks. It is also called variola. <ref>http://www.cdc.gov/vaccines/about/terms/glossary.htm#s</ref> |