monkeypox, rare disease caused by infection with the monkeypox virus, which is related to the viruses that cause smallpox and cowpox. The symptoms of monkeypox, which typically take 1 to 2 weeks to appear and last for 24 weeks, are similar to but milder than those of smallpox. Fever and chills, headache, muscle aches, and backache, and a feeling of exhaustion precede the development of swollen lympth nodes and a rash, which often first appears on the face before spreading elsewhere on the body; the rash lesions ultimately develop into pustules that open and then crust over. As many as 10% of cases result in death. There is no known treatment for monkeypox; the smallpox vaccine, antiviral drugs, and vaccinia immune globulin can be used to control an outbreak.

Human monkeypox infections occur when a person comes into contact with an infected animal or person or virus-contaminated materials such as bedding; the virus enters the body through a bite, scratch, or cut or abrasion in the skin or through the nose, mouth, or eyes. The virus is transmitted primarily by respiratory droplets, bodily fluids, or material from the lesions. Two distinct groups of monkeypox virus strains exist, Central African and West African. The latter generally results in milder cases with fewer deaths, and is not usually spread person to person.

Monkeypox was first identified in 1958 when outbreaks occurred in monkeys used for research; the disease also has been found in rodents. The first case in humans was recorded in 1970 in the Congo (Kinshasa). Monkeypox has since been reported in humans in other parts of central and W African. The only known outbreak outside Africa occurred in the United States in 2003; it was caused by a West African strain that came from small mammals imported from Ghana.

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