- a disease caused by a virus of the genus Orthopoxvirus, clinically similar to but less severe than smallpox, and transmitted to humans via contact with an infected person or animal, or with a contaminated material: first identified in humans in 1970, outbreaks historically occurred mostly in central and western Africa, with the United States in 2003 having the first confirmed cases outside of Africa, followed by global outbreaks, especially in Europe and the Americas, that became increasingly reported in the 2020s. Abbreviation: MPX
