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cowpox cow·pox (kou'pŏks')
A mild, contagious skin disease of cattle, usually affecting the udder, that is caused by a virus and characterized by the eruption of a pustular rash. When the virus is transmitted to humans, as by vaccination, it can confer immunity to smallpox. Also called vaccinia.
mildly eruptive disease of cows that when transmitted to otherwise healthy humans produces immunity to smallpox. The cowpox virus is closely related to variola, the causative virus of smallpox. The word vaccinia is sometimes used interchangeably with cowpox to refer to the human form of the disease, sometimes to refer to the causative virus, and sometimes to refer only to the artificially induced human form of cowpox.