Monkeypox overview

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Patient Info


Historical Perspective


Epidemiology & Demographics

Risk Factors


Causes of Monkeypox

Differentiating Monkeypox from other Diseases

Natural History, Complications & Prognosis


History & Symptoms

Physical Examination

Lab Tests


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Other Imaging Findings

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Medical Therapy


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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Bassel Almarie M.D.[2]


Monkeypox virus, also known as MPOX, was first identified in monkeys shipped from Singapore to Denmark in 1958[1]. First case of monkeypox in humans was reported in the Republic of the Congo in 1970[2]. Monkeypox virus is a member of orthopoxvirus genus (family Poxviridae)[3]. It can be transmitted from animal to animal, animal to human, and human to human. There is little evidence on mother-to-child transmission[4].

Historical Perspective

Monkeypox virus was first identified in monkeys shipped from Singapore to Denmark in 1958[1]. First case of monkeypox in humans was reported in a hospitalized child in the Republic of the Congo in 1970[2]. In the following years, monkeypox virus emerged and cases were recorded in 11 African countries. Until the late 1980s, more than 400 cases were recorded[5]. In the early 1990s, the number of reported cases dramatically declined to notably zero cases between 1993 and 1995[6]. In 1996, large number of cases were suspected in an outbreak in Democratic Republic of Congo but only small number of cases were laboratory confirmed[7].

In 2003, 47 confirmed and probable cases of monkeypox were in the United States. In the following years, there has been cases of monkeypox recorded periodically in non-endemic regions, predominately in the United Kingdom and one in Singapore. All of these cases were imported from endemic regions. In May 2022, case clusters of monkeypox were traced around the world over a short period of time. As of May 22, 2022, a total of 109 cases were recorded and 87 suspected around the world. On June 2, 2022, 780 cases of monkeypox were identified or reported to the World Health Organization[8]. As of June 15, 2022, a total of 2103 laboratory confirmed cases, including one death, have been reported to World Health Organization[9].


Monkeypox virus is a member of orthopoxvirus genus (family Poxviridae)[3]. The monkeypox virus genome consists of linear double-stranded DNA that multiplies in the cytoplasm of infected cell[10]. It has two genetic clades: the west African clade and the central African (Congo Basin) clade[11]. Possible routes of transmission are animal-to-animal, animal-to-human, and human-to-human. Virus is transmitted via direct contact with body fluids or lesions of infection person or animal, direct contact with contaminated materials such as clothing, and via respiratory secretions[12]. The role of vaginal fluids and semen in the transmission of the virus is still being investigated[13].


Animal-to-human transmission: The virus can be acquired through daily exposure to an infected animal or complex exposure to an infected animal (e.g. invasive bite or scratch that breaks the skin). Also through direct contact with lesions or bodily fluids of an infected animal.

Human-to-human transmission: The virus can be acquired through close physical contact with infected person, direct contact with lesions, bodily fluids, or respiratory secretions of an infected person, direct contact with contaminated materials[12], or via placenta from mother to fetus[14][15][4].

Differential Diagnosis

  • Smallpox
  • Chickenpox
  • Scabies
  • Syphilis
  • Bacterial skin infections
  • Drug-associated allergy

Epidemiology and Demographics

Precise prevalence and incidence are difficult to establish due to paucity of reporting in previous outbreaks. The median age in the the 1970s and 1980s was 4 and 5 years. In the 2000s and 2010s, the median age of monkeypox infection increased to 10 and 21 years. In May 2022, the average median age of monkeypox infections was 37 years.

Risk Factors

Risk factors for contacting monkeypox virus include close physical contact with infected person or animal (including direct contact with lesions, bodily fluids, and respiratory secretions), direct contact with contaminated materials such as towels[16][17], eating undercooked meat[18], and complex exposures to infected animal (e.g., invasive bite or scratch that breaks the skin)[19].

Complications and Prognosis

Monkeypox is usually a self-limited disease with the symptoms resolving within 2 to 4 weeks. Complications are rare. They include secondary bacterial infection such as pneumonia, sepsis, encephalitis, corneal inflammation of the eyes[20][21][22], and conjunctivitis[23].


History and Symptoms

The significant information in the patient's history include recent travel to endemic area of monkeypox or possible contact with infected person, animal, or contaminated material. Initial symptoms fever, chills, lymphadenopathy, headache, myalgia, followed by skin rash of multiple lesions that develop and evolve at the same time. The evolvement of the lesions progresses as follows: macular (1−2 days), papular (1−2 days), vesicular (1−2 days), pustular (5-7 days), lastly scab (7-14 days)[24].

Physical Examination

Depending on the stage of the disease, physical findings may include low-grade fever, enlarged lymph nodes (submental, submandibular, cervical, inguinal), and skin rash with typical progression: Macular (1-2 days), papular (1-2 days), vesicular (1-2 days), pustular (5-7 days), scabs (7-14 days)[24].

Laboratory Findings

Polymerase chain reaction (PCR) is the preferred test to confirm monkeypox virus (MPXV) given its sensitivity and accuracy. Samples should be obtained from skin lesions, precisely, the roof or fluid from vesicles and pustules, and dry crusts[25]. PCR blood tests are usually inconclusive because the does not live long in the blood[14].


There are no EKG findings associated with monkeypox.


Ultrasound may be helpful to assess the fetus well-being in pregnant women with laboratory confirmed monkeypox[15].

Other Diagnostic Studies


Medical Therapy

Currently, there is no proven, safe treatment for monkeypox. To contain the outbreak, the CDC advises using smallpox vaccine, cidofovir, ST-246, and vaccinia immune globulin. Vaccines are not available to public as for now but in an event of larger outbreak, the CDC will establish guidelines on who to receive the vaccine.

Surgical Therapy

Surgery is not indicated for monkeypox. Monkeypox is usually a self-limiting disease with symptoms lasting from two to four weeks[14].

Primary Prevention

The Advisory Committee on Immunization Practices recommends ACAM2000 or JYNNEOS as pre-exposure prophylaxis to individuals at risk of exposure to monkeypox on basis of an occupational assessment[26].

The CDC recommends proper hand hygiene with soap and water or alcohol-based hand sanitizers after contact with infected animals or humans. Avoid contact with animals that can act as a reservoir for the virus, e.g. rodents. Avoid close contact with lesions, bodily fluids, or respiratory droplets, or contaminated materials such as bedding or towels. Personal protective equipment (PPE) is essential for healthcare workers when handling patients. Isolate infected patients to reduce spread[27].


  1. 1.0 1.1 Cho CT, Wenner HA (1973). "Monkeypox virus". Bacteriol Rev. 37 (1): 1–18. doi:10.1128/br.37.1.1-18.1973. PMC 413801. PMID 4349404.
  2. 2.0 2.1 Ladnyj ID, Ziegler P, Kima E (1972). "A human infection caused by monkeypox virus in Basankusu Territory, Democratic Republic of the Congo". Bull World Health Organ. 46 (5): 593–7. PMC 2480792. PMID 4340218.
  3. 3.0 3.1 "ICTV".
  4. 4.0 4.1 Kisalu NK, Mokili JL (2017). "Toward Understanding the Outcomes of Monkeypox Infection in Human Pregnancy". J Infect Dis. 216 (7): 795–797. doi:10.1093/infdis/jix342. PMC 6279131. PMID 29029238.
  5. Sklenovská N, Van Ranst M (2018). "Emergence of Monkeypox as the Most Important Orthopoxvirus Infection in Humans". Front Public Health. 6: 241. doi:10.3389/fpubh.2018.00241. PMC 6131633. PMID 30234087.
  6. Heymann DL, Szczeniowski M, Esteves K (1998). "Re-emergence of monkeypox in Africa: a review of the past six years". Br Med Bull. 54 (3): 693–702. doi:10.1093/oxfordjournals.bmb.a011720. PMID 10326294.
  7. Hutin YJ, Williams RJ, Malfait P, Pebody R, Loparev VN, Ropp SL; et al. (2001). "Outbreak of human monkeypox, Democratic Republic of Congo, 1996 to 1997". Emerg Infect Dis. 7 (3): 434–8. doi:10.3201/eid0703.010311. PMC 2631782. PMID 11384521.
  8. "Multi-country monkeypox outbreak: situation update".
  9. Glenn JK, Goldman J, Bonaventura J, Bonaventura C, Sullivan B, Godette G (January 1976). "Task delegation to physician extenders--some comparisons". Am J Public Health. 66 (1): 64–6. doi:10.2105/ajph.66.1.64. PMC 1653348. PMID 2022.
  10. Holland J, Domingo E (1998). "Origin and evolution of viruses". Virus Genes. 16 (1): 13–21. doi:10.1023/a:1007989407305. PMID 9562888.
  11. Likos AM, Sammons SA, Olson VA, Frace AM, Li Y, Olsen-Rasmussen M; et al. (2005). "A tale of two clades: monkeypox viruses". J Gen Virol. 86 (Pt 10): 2661–2672. doi:10.1099/vir.0.81215-0. PMID 16186219.
  12. 12.0 12.1 "CDC Monkeypox Response: Transmission | CDC Online Newsroom | CDC".
  13. "U.S. Monkeypox Outbreak 2022: Situation Summary | Monkeypox | Poxvirus | CDC".
  14. 14.0 14.1 14.2 "Monkeypox". Retrieved 2022-06-15.
  15. 15.0 15.1 Khalil A, Samara A, O'Brien P, Morris E, Draycott T, Lees C; et al. (2022). "Monkeypox and pregnancy: what do obstetricians need to know?". Ultrasound Obstet Gynecol. doi:10.1002/uog.24968. PMID 35652380 Check |pmid= value (help).
  16. "Multi-country monkeypox outbreak in non-endemic countries".
  17. Centers for Disease Control and Prevention (CDC) (2003). "Update: multistate outbreak of monkeypox--Illinois, Indiana, Kansas, Missouri, Ohio, and Wisconsin, 2003". MMWR Morb Mortal Wkly Rep. 52 (27): 642–6. PMID 12855947.
  18. Reynolds MG, Davidson WB, Curns AT, Conover CS, Huhn G, Davis JP; et al. (2007). "Spectrum of infection and risk factors for human monkeypox, United States, 2003". Emerg Infect Dis. 13 (9): 1332–9. doi:10.3201/eid1309.070175. PMC 2857287. PMID 18252104.
  19. Reynolds MG, Yorita KL, Kuehnert MJ, Davidson WB, Huhn GD, Holman RC; et al. (2006). "Clinical manifestations of human monkeypox influenced by route of infection". J Infect Dis. 194 (6): 773–80. doi:10.1086/505880. PMID 16941343.
  20. Jezek Z, Grab B, Szczeniowski M, Paluku KM, Mutombo M (1988). "Clinico-epidemiological features of monkeypox patients with an animal or human source of infection". Bull World Health Organ. 66 (4): 459–64. PMC 2491168. PMID 2844428.
  21. Learned LA, Reynolds MG, Wassa DW, Li Y, Olson VA, Karem K; et al. (2005). "Extended interhuman transmission of monkeypox in a hospital community in the Republic of the Congo, 2003". Am J Trop Med Hyg. 73 (2): 428–34. PMID 16103616.
  22. Huhn GD, Bauer AM, Yorita K, Graham MB, Sejvar J, Likos A; et al. (2005). "Clinical characteristics of human monkeypox, and risk factors for severe disease". Clin Infect Dis. 41 (12): 1742–51. doi:10.1086/498115. PMID 16288398.
  23. "Redirecting". Retrieved 2022-06-14.
  24. 24.0 24.1 "Clinical Recognition | Monkeypox | Poxvirus | CDC". Retrieved 2022-06-14.
  25. "Laboratory testing for the monkeypox virus: Interim guidance". Retrieved 2022-06-15.
  26. Rao AK, Petersen BW, Whitehill F, Razeq JH, Isaacs SN, Merchlinsky MJ; et al. (2022). "Use of JYNNEOS (Smallpox and Monkeypox Vaccine, Live, Nonreplicating) for Preexposure Vaccination of Persons at Risk for Occupational Exposure to Orthopoxviruses: Recommendations of the Advisory Committee on Immunization Practices - United States, 2022". MMWR Morb Mortal Wkly Rep. 71 (22): 734–742. doi:10.15585/mmwr.mm7122e1. PMID 35653347 Check |pmid= value (help).
  27. "Prevention | Monkeypox | Poxvirus | CDC". Retrieved 2022-06-16.

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