pox disease, any of a complex of viral diseases in human beings and domestic animals, marked chiefly by eruptions of the skin and mucous membranes. Sheep pox and rabbit pox are spread by airborne infectious particles that are inhaled. Horse pox, fowl pox, and mouse pox usually are spread by skin contact. Cowpox (vaccinia) and pseudocowpox (paravaccinia), localized on the udder and teats of cows, are transmissible to human beings by skin contact. Horse pox (contagious pustular stomatitis) is now rare. Swine pox, of two types, is prevalent but rarely fatal. Sheep pox, the most severe pox disease of domestic animals, and goat pox are now confined to parts of southeastern Europe, North Africa, and Asia.
Effective vaccines are available for most pox diseases, though outbreaks have continued. Buffalopox was reported in Maharashtra, India, in the 1990s. Monkeypox, which was first identified in 1958 and found primarily in Africa, was cited in the United States in 2003.
Smallpox, a pox disease known in human beings as early as 1122 bc, was declared eradicated in 1979. In 2000 accidental exposure to smallpox vaccine (made from a virus related to smallpox) resulted in an isolated outbreak in Russia. Only two laboratories—in Russia and in the United States—were known to have live samples of smallpox in the 21st century.