Monkeypox is an orthopoxvirus, related to smallpox and cowpox, that is normally endemic in parts of western and central Africa. Occasional sporadic cases have been previously described outside of Africa.

In May 2022, multiple regions of Europe and North America reported clusters of monkeypox cases.

Last updated May 24, 2022

Epidemiology and virology

Very large, enveloped, double-stranded DNA virus (can be seen with light microscopy):

  • First identified in research primates, but natural reservoir may actually be rodents
  • Transmission via close contact with skin lesions, body fluids, respiratory droplets, and contaminated materials (such as linen)
  • First human case identified in Democratic Republic of Congo (DRC) in 1970; endemic in DRC, Nigeria, Sierra Leone
  • Approximately 200 cases in Nigeria reported since 2017
  • Prior US outbreak in 2003 (47 confirmed and probable cases associated with exposure to imported animals)

Clinical features

  • Symptoms similar to classic smallpox but milder
  • Incubation usually 7 to 14 days before onset of fever
  • Fever, myalgia, and lymphadenopathy, followed 1 to 2 days later by lesions in mouth and on skin
  • Rash presents sequentially with macules, then papules, followed by vesicles or pustules that are deep-seated, firm, and well-circumscribed
  • Genital lesions reported in recent outbreak
  • Illness typically lasts 2 to 4 weeks
  • Contagious from the onset of the rash and oral lesions, and lasts until these lesions have scabbed over
  • Case fatality rate in West Africa estimated at 3% to 4%, with risk highest in children, young adults, immunocompromised persons


  • Contact local public health authorities immediately for suspected cases and to coordinate testing
  • Standard, contact, and airborne precautions recommended in all health care settings for suspected cases
  • Although airborne transmission is not described, similarly presenting pathogens (eg, varicella, other poxviruses) could be airborne
  • Drug treatment for severe cases:
    • Tecovirimat
    • Cidofovir
    • Brincidofovir


  • Smallpox vaccination is estimated to be at least 85% protective against monkeypox
  • Vaccination can be effective as postexposure prophylaxis
  • Two approved vaccines in the US, Europe:
    • Jynneos (Bavarian Nordic) – nonreplicating vaccinia virus vector, two-dose series, approved for smallpox and monkeypox
    • ACAM2000 – live attenuated vaccinia strain; contraindicated in immunocompromised hosts, persons with eczema, and their close contacts
  • Vaccinia immune globulin (VIG)