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Recognizing monkeypox


Photo of monkeypox virus

The information on this page was created by the Academy’s Ad Hoc Task Force to Develop Monkeypox Content.

Monkeypox is caused by the monkeypox virus, which belongs to the Orthopoxvirus genus in the family Poxviridae.1 Though monkeypox is rare, it is endemic in Central and West African countries, and though surveillance of this disease can be challenging, the number of cases have increased in recent decades and outbreaks have occurred more recently in non-endemic countries.2-6

There are two distinctive clades of the virus: the West African and the Congo Basin (or Central African). The Congo Basin clade (a group of similar viruses based on genetic sequences) is thought to cause more severe disease and be more lethal than the West African clade.7-9 The current virus seen in cases in the U.S. is the less severe West African clade. Despite the name, the reservoir species for monkeypox is unknown, though non-human primates remain susceptible to the disease, along with many other mammals including rodents.1,7,10 The most recent prior U.S. outbreak in 2003 was traced to infected prairie dogs, and there are concerns that if this outbreak is able to infect rodents, a persistent reservoir could develop leading to ongoing sporadic outbreaks in the future. Monkeypox can be transmitted from animal to human (zoonotic) or human to human.11 Transmission can occur through large respiratory droplets (theoretical risk of airborne transmission but not as contagious as SARS-CoV-2), body fluids, skin lesions (contact), and contaminated items.1,11 Contact during sex can spread monkeypox, but it is not classically a sexually transmitted disease — it is simply that during sex, there is skin to skin contact and shared air.

The incubation period for monkeypox is usually 7-14 days but can span up to 21 days.1 Initial signs and symptoms of monkeypox can include: fever; headache; maxillary, cervical, or inguinal lymphadenopathy; back pain; muscle aches; chills; sore throat; cough; and exhaustion.1,4,6,12

Within 1-3 days after fever appears, cases develop a rash. This rash generally starts on the face and extremities (including palms and soles of the feet), and spreads to other parts of the body.1,12 The rash evolves from macules, to papules, to vesicles, to pustules before scabbing and eventually crusting over.1,12 Lesions are often noted in the oral mucous membranes and can cause difficulties with drinking and eating.6,12 These can also develop in the conjunctivae and cornea, as well as groin and genitals.11,12 During this current outbreak, it has been reported that cases in the current monkeypox outbreak have presented differently, with minimal symptoms prior to rash development, and rash originating in the groin area.13 Confirmed cases of monkeypox should be isolated until lesions have crusted over and a fresh layer of skin has formed underneath.4 Pitted scars, hyperpigmentation and/or hypopigmentation skin may remain after the crusts have fallen off. Once all crusts have fallen off, a person is no longer contagious. Generally, the duration of diseases is between 2-4 weeks.1,14 Case-fatality rates for the West African clade are estimated to be around 3.6%, though this varies by clade and access to supportive care, with lower case fatality rates reported in prior U.S. outbreaks (and no deaths in the most recent U.S. outbreak).5,6,14,15

There are a number of differential diagnoses for monkeypox, including varicella, secondary syphilis, herpes, chancroid, measles, scabies, hand-foot-mouth, and medication-associated allergies.1,12 Lymphadenopathy is a distinctive feature of monkeypox compared to some of the other differential diagnoses, though chancroid, and advanced or severe cases of other entities, may develop lymphadenopathy.12

Varicella zoster virus, unlike monkeypox, belongs to the α-Herpesviridae family.16 Chickenpox from varicella-zoster virus tends to develop more rapidly than monkeypox and eruptions and individual vesicles are less severe, and usually evolve pleomorphically in a centripetal distribution.6,8,17 Further, varicella lesions rarely present on the palms and soles of the feet.6,17

The virus that causes smallpox (variola virus) also belongs to the family Poxviridae. Like monkeypox virus, variola virus belongs to the genus Orthopoxvirus.18,19, 20 Individuals who are vaccinated for smallpox may be at reduced risk for monkeypox.6 Routine vaccination for smallpox was halted in the U.S. in 1972, and most physicians under the age of 50 are unvaccinated.21 The rash associated with smallpox is similar to that of monkeypox and progresses through similar phases.14 However, unlike smallpox, monkeypox lesions are crop-like and have a mild centrifugal spread.11 Further, as stated above, lymphadenopathy associated with monkeypox is not typical to smallpox.8,12

The smallpox vaccination has been shown to be approximately 85% effective in preventing monkeypox, however the number of people who have received this has declined since the eradication of smallpox.1,12 There is currently one FDA approved vaccine for the prevention of monkeypox, which is currently under evaluation for the protection of individuals at increased risk of exposure to orthopoxviruses.1 For close contacts of confirmed cases, one control method that is being evaluated is “ring vaccination” for individuals who had close contact with that case.21


Frequently asked questions
Q. What is the role of the dermatologist?


A. As dermatologists, we may be called on to identify possible cases of monkeypox (or other papulovesicular/vesiculopustular entities), and we may also be called on to perform a viral swab for PCR testing of a skin lesion. Swabs of the surface and/or exudate, roofs from more than one lesion, or lesion crusts are recommended for laboratory confirmation of monkeypox.21 If you have a suspected case of monkeypox, contact the state health department for state-specific guidance on specimen collection.

Q. Is there any treatment for monkeypox?


A. There is no specific treatment FDA-approved for monkeypox at this time.1 Symptoms usually resolve on their own, though patients should take care of their rash by allowing it to dry or applying a moist dressing.23 There are currently several experimental antiviral treatments for monkeypox, though there is limited data as to who may benefit from these treatments.1

Q. What PPE should I wear?


A. The current recommendations for PPE for possible and confirmed monkeypox cases by the CDC1 are as follows:

  • Gown

  • Gloves

  • NIOSH approved N-95

  • Eye protection

Q. I have been taking care of a patient with monkeypox. What should I do?


A. Use of PPE should be protective in most circumstances. If there is concern for a high-risk exposure, it may be possible to be vaccinated after exposure to monkeypox. The CDC recommends vaccination within four days of a high-risk exposure to prevent onset of disease, or vaccination up to two weeks after the date of exposure to help reduce symptoms of disease.1 Please contact your local infection control personnel and/or state health department for more information. Recommendations vary based on risk-level of exposure (including type of PPE, duration, and length of exposure), and state public health guidelines in this area are fluid.

Q. How does the West variant of monkeypox death rate compare to smallpox?


A. Historically, the case-fatality rate of smallpox was estimated to be as high as 30%. In comparison, the case-fatality rate of the West African clade of monkeypox is estimated to be 3.6%, but there have been no reported deaths in recent U.S. outbreaks, possibly due to the level of supportive care available.5,24

Q. How long after vaccination is the smallpox vaccine effective against monkeypox? Is the protection lifelong?


A. In individuals historically vaccinated for smallpox with the Dryvax vaccine, antiviral antibody and T-cell response may be maintained for up to 75 years against smallpox. Research has shown that the duration of monkeypox immunity from the smallpox vaccination varies, but some level of protection may be offered long after an individual has been vaccinated.25

Q. At what point does an individual with monkeypox become infectious to others incubation, systemic symptoms such as fever, or only once the rash develops?


A. According to the CDC, individuals are not contagious during the incubation period. Individuals may be contagious during initial symptom onset and are contagious from the rash phase of the disease until the lesions are completely crusted over.1

Q. Where do I send a PCR test if I have a suspected case?


A. Please contact your local hospital epidemiologist, infection control personnel, and/or state health department, as different locations will have different regulations on where to send the test. If appropriate, the state health department will contact the Centers for Disease Control and Prevention (CDC).1

Q. Where can I find out more information about the role of smallpox vaccination for monkeypox?


A. See CDC guidance on smallpox and monkeypox vaccines, including administration guidance after exposure to monkeypox.

Q. Where do I find CDC information on monkeypox?


A. Access the CDC page on monkeypox for clinicians.

Other Resources:

References
  1. Centers for Disease Control and Prevention. Monkeypox. Accessed May 24, 2022. https://www.cdc.gov/poxvirus/monkeypox/index.html

  2. Ihekweazu C, Yinka-Ogunleye A, Lule S, Ibrahim A. Importance of epidemiological research of monkeypox: is incidence increasing? Expert Rev Anti Infect Ther. 2020;18(5):389-392. doi:10.1080/14787210.2020.1735361

  3. Bankuru SV, Kossol S, Hou W, Mahmoudi P, Rychtář J, Taylor D. A game-theoretic model of Monkeypox to assess vaccination strategies. PeerJ. 2020;8:e9272. Published 2020 Jun 22. doi:10.7717/peerj.9272

  4. World Health Organization. Multi-country monkeypox outbreak in non-endemic countries. Accessed May 24, 2022. https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON385

  5. Bunge EM, Hoet B, Chen L, et al. The changing epidemiology of human monkeypox-A potential threat? A systematic review. PLoS Negl Trop Dis. 2022;16(2):e0010141. Published 2022 Feb 11. doi:10.1371/journal.pntd.0010141

  6. McCollum AM, Damon IK. Human monkeypox [published correction appears in Clin Infect Dis. 2014 Jun;58(12):1792]. Clin Infect Dis. 2014;58(2):260-267. doi:10.1093/cid/cit703

  7. Silva NIO, de Oliveira JS, Kroon EG, Trindade GS, Drumond BP. Here, There, and Everywhere: The Wide Host Range and Geographic Distribution of Zoonotic Orthopoxviruses. Viruses. 2020;13(1):43. Published 2020 Dec 30. doi:10.3390/v13010043

  8. Kantele A, Chickering K, Vapalahti O, Rimoin AW. Emerging diseases-the monkeypox epidemic in the Democratic Republic of the Congo. Clin Microbiol Infect. 2016;22(8):658-659. doi:10.1016/j.cmi.2016.07.004

  9. Likos AM, Sammons SA, Olson VA, et al. A tale of two clades: monkeypox viruses. J Gen Virol. 2005;86(Pt 10):2661-2672. doi:10.1099/vir.0.81215-0

  10. Durski KN, McCollum AM, Nakazawa Y, et al. Emergence of Monkeypox - West and Central Africa, 1970-2017 [published correction appears in MMWR Morb Mortal Wkly Rep. 2018 Apr 27;67(16):479]. MMWR Morb Mortal Wkly Rep. 2018;67(10):306-310. Published 2018 Mar 16. doi:10.15585/mmwr.mm6710a5

  11. Alakunle E, Moens U, Nchinda G, Okeke MI. Monkeypox Virus in Nigeria: Infection Biology, Epidemiology, and Evolution. Viruses. 2020;12(11):1257. Published 2020 Nov 5. doi:10.3390/v12111257

  12. World Health Organization. Monkeypox: Key Facts. Accessed May 24, 2022. https://www.who.int/news-room/fact-sheets/detail/monkeypox

  13. Harris E. What to Know About Monkeypox [published online ahead of print, 2022 May 27]. JAMA. 2022;10.1001/jama.2022.9499. doi:10.1001/jama.2022.9499

  14. Damon IK. Status of human monkeypox: clinical disease, epidemiology and research. Vaccine. 2011;29 Suppl 4:D54-D59. doi:10.1016/j.vaccine.2011.04.014

  15. Simpson K, Heymann D, Brown CS, et al. Human monkeypox - After 40 years, an unintended consequence of smallpox eradication. Vaccine. 2020;38(33):5077-5081. doi:10.1016/j.vaccine.2020.04.062

  16. Pergam SA, Limaye AP; AST Infectious Diseases Community of Practice. Varicella zoster virus (VZV) in solid organ transplant recipients. Am J Transplant. 2009;9 Suppl 4(Suppl 4):S108-S115. doi:10.1111/j.1600-6143.2009.02901.x

  17. Leung J, McCollum AM, Radford K, et al. Varicella in Tshuapa Province, Democratic Republic of Congo, 2009-2014. Trop Med Int Health. 2019;24(7):839-848. doi:10.1111/tmi.13243

  18. Babkin IV, Babkina IN. The origin of the variola virus. Viruses. 2015;7(3):1100-1112. Published 2015 Mar 10. doi:10.3390/v7031100

  19. Centers for Disease Control and Prevention. Poxvirus. Accessed May 24, 2022. https://www.cdc.gov/poxvirus/index.html

  20. Efridi W, Lappin SL. Poxviruses. [Updated 2022 Apr 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK558959/

  21. Centers for Disease Control and Prevention. Smallpox. Accessed May 26, 2022. https://www.cdc.gov/smallpox/index.html

  22. World Health Organization. Laboratory testing for the monkeypox virus: Interim Guidance. Accessed May 26, 2022. https://www.who.int/publications/i/item/WHO-MPX-laboratory-2022.1

  23. World Health Organization. Monkeypox: Questions and answers. Accessed May 31, 2022. https://www.who.int/news-room/questions-and-answers/item/monkeypox

  24. Food and Drug Administration. Smallpox. Accessed May 26, 2022. https://www.fda.gov/vaccines-blood-biologics/vaccines/smallpox

  25. Hammarlund E, Lewis MW, Carter SV, et al. Multiple diagnostic techniques identify previously vaccinated individuals with protective immunity against monkeypox. Nat Med. 2005;11(9):1005-1011. doi:10.1038/nm1273

Additional resources

Globalization of monkeypox

Read the May 2022 DermWorld Insights & Inquiries article on monkeypox.

CDC health alert

Read the CDC's Health Alert Network (HAN) update on monkeypox.

Situation summary

Access the CDC monkeypox situation summary.

Clinical recognition

See the CDC page on monkeypox clinical recognition.

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