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Stuart N Isaacs, MD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Monkeypox is a viral zoonotic infection that results in a rash similar to smallpox. However, the person-to-person spread and the mortality from a monkeypox infection are significantly lower than for smallpox. Clinically, these two viral infections are difficult to distinguish, raising concerns that monkeypox could be used for bioterrorism [1]. (See "The epidemiology, pathogenesis, and clinical manifestations of smallpox" and "Identifying and managing casualties of biological terrorism".)

This topic will review the virology, epidemiology, clinical manifestations, diagnosis and treatment of monkeypox.


Monkeypox, an orthopoxvirus, was first isolated in the late 1950s from a colony of sick monkeys. The virus is in the same genus as variola (causative agent of smallpox) and vaccinia viruses (the virus used in smallpox vaccine). Electron microscopy of cells infected with monkeypox virus shows a brick-like virion, indistinguishable from the virions of variola or vaccinia viruses (picture 1).

Two distinct strains of monkeypox exist in different geographic regions of Africa, as suggested by epidemiologic, animal, and molecular evidence [2]. In comparison to strains isolated from Central Africa, monkeypox from Western Africa is less virulent and lacks a number of genes present in the other viral strain [2,3].


History — It is believed that monkeypox virus has infected humans for thousands of years in sub-Saharan Africa [1].


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Literature review current through: Sep 2016. | This topic last updated: Aug 11, 2015.
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