Recognizing mpox

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

Mpox (monkeypox) is caused by the mpox virus, which belongs to the Orthopoxvirus genus in the family Poxviridae.¹ Though mpox 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

A registry to gather information about dermatologic manifestations of mpox, as well as skin reactions to the mpox vaccine, has been launched. The registry is an effort on behalf of the American Academy of Dermatology and the International League of Dermatologic Societies. Cases can be entered by all health care professionals taking care of either (a) patients with mpox or (b) patients who have received a smallpox/mpox vaccine and developed a skin reaction that you wish to report.

Learn more or enter a case.

There are two distinctive clades of the virus: Clade I and Clade II (formerly known as the Congo Basin and West African clades). Clade I is thought to cause more severe disease and be more lethal than Clade II.^7-9 The current virus seen in cases in the U.S. is the less severe Clade II. Despite the name, the reservoir species for mpox 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. Mpox 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 mpox, 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 mpox is usually 7-14 days but can span up to 21 days.¹ Initial signs and symptoms of “classic” mpox can include: fever; headache; maxillary, cervical, or inguinal lymphadenopathy; back pain; muscle aches; chills; sore throat; cough; and exhaustion.^1,4,6,12

Access a Dialogues in Dermatology bonus episode on mpox.

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 anogenital area.^11-13

Cases in the current mpox outbreak have presented differently, with minimal symptoms prior to rash development, and rash originating in the anogenital and oral areas, as accompanied with anal pain, tenesmus, proctitis, and oropharyngeal pain. The pain is often more severe than the clinical findings would suggest.^13-15 A recent study found that the most common locations of lesions were the anogenital area (73%); trunk, arms, or legs (55%); face (25%); and palms and soles (10%). Most persons had fewer than 10 lesions and almost 10% presented with a single genital lesion.²⁸

Confirmed cases of mpox should be isolated until lesions have crusted over and a fresh layer of skin has formed underneath.⁴ Pitted scars, hyperpigmentation and/or hypopigmentation 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.^1,16 Case-fatality rates for Clade II 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, to date).^5,6,16,17

There are a number of differential diagnoses for mpox, including varicella, secondary syphilis, herpes, chancroid, measles, scabies, hand-foot-mouth, and medication-associated allergies.^1,12 Lymphadenopathy is a distinctive feature of mpox 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 mpox, belongs to the α-Herpesviridae family.¹⁸ Chickenpox from varicella-zoster virus tends to develop more rapidly than mpox and eruptions and individual vesicles are less severe, and usually evolve pleomorphically in a centripetal distribution.^6,8,19 Further, varicella lesions rarely present on the palms and soles of the feet.^6,19

The virus that causes smallpox (variola virus) also belongs to the family Poxviridae. Like mpox virus, variola virus belongs to the genus Orthopoxvirus.^20-22 Individuals who are vaccinated for smallpox may be at reduced risk for mpox.⁶ Routine vaccination for smallpox was halted in the U.S. in 1972, and most physicians under the age of 50 are unvaccinated.²³ The rash associated with smallpox is similar to that of mpox and progresses through similar phases.¹⁶ However, unlike smallpox, mpox lesions are crop-like and have a mild centrifugal spread.¹¹ Further, as stated above, lymphadenopathy associated with mpox is not typical in smallpox.^8,12

Smallpox vaccination has been shown to be approximately 85% effective in preventing mpox, 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 mpox, 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.²³

The FDA issued an Emergency Use Authorization (EUA) for the JYNNEOS vaccine to allow clinicians to use the vaccine by intradermal injection for individuals aged 18 years or older who are determined to be at high risk for mpox infection. This is expected to increase the total number of doses available for use by up to 5-fold. The lower dose is immunologically noninferior to the standard dose, but it is more reactogenic.

CPT codes for mpox testing and vaccination are now available. Learn more in Derm Coding Consult.

Frequently asked questions

Q. What is the role of the dermatologist?

A. As dermatologists, we may be called on to identify possible cases of mpox, 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 or lesion crusts are recommended for laboratory confirmation of mpox.²⁴ Current guidance indicates that it is not necessary to de-roof the lesion before swabbing.¹ If you have a suspected case of mpox, contact your state health department for state-specific guidance on specimen collection.

Q. Is there any treatment for mpox?

A. There is no specific FDA-approved treatment for mpox 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.²⁵ There are currently several experimental antiviral treatments for mpox, though there is limited data as to who may benefit from these treatments.¹ Tecovirimat (TPOXX) is an antiviral medication that may be useful for individuals with severe cases of mpox and those who are infected with mpox and are at risk of severe disease.¹ Please see the link below to read more about how health care providers can obtain and use TPOXX.

Q. What PPE should I wear?

A. The current recommendations for PPE for possible and confirmed mpox 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 mpox. 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 mpox. 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. What should I do if I suspect my patient has mpox?

A. If you suspect that your patient may have mpox, isolate the patient and contact your state health department or the CDC’s Emergency Operations Center (770-488-7100) for next steps.¹ The CDC’s Isolation and Exposure Monitoring guidance may be used to help counsel patients on how to monitor symptoms and reduce the risk of transmission to others.

Q. How does the Clade II mpox 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 Clade II of mpox 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.^5,26

Q. How long after vaccination is the smallpox vaccine effective against mpox? 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 mpox immunity from the smallpox vaccination varies, but some level of protection may be offered long after an individual has been vaccinated.²⁷

Q. At what point does an individual with mpox 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 mpox?

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

Q. Where do I find CDC information on mpox?

A. Access the CDC page on mpox for clinicians.

Other Resources:

References

Centers for Disease Control and Prevention. Monkeypox. Accessed August 3, 2022. https://www.cdc.gov/poxvirus/monkeypox/index.html
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
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
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
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
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
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
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
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
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
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
World Health Organization. Monkeypox: Key Facts. Accessed May 24, 2022. https://www.who.int/news-room/fact-sheets/detail/monkeypox
Bragazzi NL, Kong JD, Mahroum N, et al. Epidemiological trends and clinical features of the ongoing monkeypox epidemic: A preliminary pooled data analysis and literature review [published online ahead of print, 2022 Jun 12]. J Med Virol. 2022;10.1002/jmv.27931. doi:10.1002/jmv.27931
Thornhill JP, Barkati S, Walmsley S, et al. Monkeypox Virus Infection in Humans across 16 Countries - April-June 2022 [published online ahead of print, 2022 Jul 21]. N Engl J Med. 2022;10.1056/NEJMoa2207323. doi:10.1056/NEJMoa2207323
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
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
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
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
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
Babkin IV, Babkina IN. The origin of the variola virus. Viruses. 2015;7(3):1100-1112. Published 2015 Mar 10. doi:10.3390/v7031100
Centers for Disease Control and Prevention. Poxvirus. Accessed May 24, 2022. https://www.cdc.gov/poxvirus/index.html
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/
Centers for Disease Control and Prevention. Smallpox. Accessed May 26, 2022. https://www.cdc.gov/smallpox/index.html
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
World Health Organization. Monkeypox: Questions and answers. Accessed May 31, 2022. https://www.who.int/news-room/questions-and-answers/item/monkeypox
Food and Drug Administration. Smallpox. Accessed May 26, 2022. https://www.fda.gov/vaccines-blood-biologics/vaccines/smallpox
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
del Rio C, Malani PN. Update on the Monkeypox Outbreak. JAMA. Published online August 11, 2022. doi:10.1001/jama.2022.14857

Additional resources

Specimen collection

See guidance from the CDC on mpox specimen collection.

Specimen submission form

Download the CDC mpox specimen submission form.

Globalization of mpox

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

CDC health alert

Read the CDC’s Health Alert Network (HAN) update on mpox.

Situation summary

Access the CDC mpox situation summary.

Clinical recognition

See the CDC page on mpox clinical recognition.

State department of health

If you see a patient who may have mpox, you should contact the health department. Access contact information from the CDC.

Treating mpox with tecovirimat (TPOXX)

Access CDC information on obtaining TPOXX from the national stockpile to treat mpox.

CDC Dear Colleague Letter

CDC Director Rochelle Walensky, MD, MPH, asks her medical colleagues to report the pain experiences of their patients with mpox.

Mpox