Smallpox

Article By:

Breman, Joel G. Division of Parasitic Diseases, Centers for Disease Control, Department of Health and Human Services, Atlanta, Georgia.

Last reviewed:June 2019

DOI:https://doi.org/10.1036/1097-8542.628900

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• Smallpox, published June 2014:Download PDF Get Adobe Acrobat Reader

An acute infectious viral disease characterized by severe systemic involvement and a single crop of skin lesions that proceeds through macular, papular, vesicular, and pustular stages. Smallpox is caused by the variola virus (see illustration), a brick-shaped, deoxyribonucleic acid (DNA)–containing member of the Poxviridae family. Strains of variola virus are indistinguishable antigenically, but have differed in the clinical severity of the disease caused. From at least 1157 BC, when the disease probably killed the Egyptian Pharaoh Ramses V, hundreds of millions of cases and millions of deaths due to smallpox occurred throughout the world. On October 26, 1977, Ali Maow Maalin, a cook from Merca, Somalia, had onset of the smallpox rash; he was the last patient to contract the disease through natural transmission, although a laboratory outbreak of smallpox occurred in the United Kingdom in 1978. Following a 13-year worldwide campaign coordinated by the World Health Organization (WHO), smallpox was declared eradicated by the World Health Assembly in May 1980. Note that smallpox is the first human disease to be eradicated. See also: Antigen; Exotic viral diseases; Infectious disease; Public health; Virus; Virus classification

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