M onkeypox, caused by monkeypox virus (MPXV), a member of the Orthopoxvirus genus, was considered a rare emerging disease before a multinational outbreak was identified in May 2022 (1).After global smallpox eradication in 1977, monkeypox became the most concerning human Orthopoxvirus infection. Clinical manifestations of monkeypox typically resemble those of smallpox, including a febrile prodrome and subsequent disseminated maculopapular rash, including vesicles and pustules, that occurs in successive stages (2). Lymphadenopathy is a prominent feature of monkeypox and usually does not occur for smallpox and chickenpox (3). Illness is less severe and death less likely among monkeypox cases than smallpox cases, but monkeypox mortality rates vary and are higher for clade I (formerly the Congo Basin clade) than for clade II (formerly the West African clade) viruses (2). Prior smallpox vaccination can confer cross-immunity for monkeypox, but smallpox vaccination programs worldwide ended in the early 1980s (4).In 1970, a human monkeypox case was reported from Basankusu, Equateur Province, Democratic Republic of the Congo (DRC) (5). Subsequent sporadic monkeypox cases were reported among human and animal populations from remote areas of Central Africa during the 1970s and 1980s (6,7). Since 1990, increases in the frequency and scale of epidemics in Africa have been reported for clade I and, to a lesser extent, since 2000 for clade II. Since 2016, confirmed monkeypox cases have been reported in DRC, Central African Republic (CAR), Republic of Congo (hereafter Congo), Nigeria, Sierra Leone, Liberia, and Cameroon (6). The true burden, circulation rates, and geographic range of this emerging disease remain unknown because many countries lack systematic routine monkeypox surveillance and affected areas often are remote (8,9).An outbreak of human monkeypox disease occurred outside Africa in 2003, after infected animals from Ghana were imported into the United States
