Mpox (Monkeypox): Symptoms, Treatment, and Outcome — DermNet (2024)

Mpox (Monkeypox) — extra information

Infections

Last Reviewed: August, 2024

Authors: Marika Gilbourne, Nottingham University, England; Chief Editor: Dr Amanda Oakley, Dermatologist, New Zealand; updated by Dr Ian Coulson, Dermatologist, UK, October 2023 and August 2024.

What is mpox?

Mpox is a rare disease caused by the DNA monkeypox virus (also known as monkeypox and MPV). The monkeypox virus belongs to the Orthopoxvirus genus — the same family of viruses as cowpox and smallpox. Infection with the MPV virus causes a rash similar to that of chickenpox.

Mpox gets its name from the discovery of the virus in monkeys under investigation in a research lab in Denmark in 1958. The first reported infection of humans was in the Democratic Republic of the Congo in 1970.

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Who gets mpox?

There are two principal strains (clades) of the mpox virus that produce sporadic outbreaks in Africa (numbering 1 to 2 thousand cases a year); a more virulent strain in the Congo basin and a milder strain in West Africa. In endemic areas, most sufferers are thought to acquire the disease from exposure to infected animal carcasses, meat, or blood (animal-to-human transmission). The average age at presentation has increased in the last two decades from 4 to 21 years. The disease is most frequent in the Democratic Republic of the Congo (DRC).

Isolated outbreaks outside Africa have mostly been related to infected animal importation but person-to-person spread has increased via direct contact with body fluids, large respiratory droplets, and contaminated linen and bedding being implicated in transmission.

From late July 2022 to May 2023, the world health organisation (WHO) labelled mpox a public health emergency of international concern. The majority of cases (86%) were from the European region (approx. 2900 cases) followed by the Americas (approx. 380), African region (73), Eastern Mediterranean Region (15), and Western Pacific Region (11). Person-to-person spread is evident from close physical proximity or sexual activity, predominantly in men who have sex with men. So far all cases have been linked to the less virulent West African strain. Fomites may be an important mode of transfer from active mpox lesions.

In August 2024, WHO once again declared mpox a public health emergency of international concern. This was in response to the growing number of mpox cases in the DRC and other African countries (Rwanda and Kenya). To date, the responsible variant is clade 1b; it seems to be more infectious than the clade 2 variant in the 2022 outbreak, spreading readily by both sexual and casual skin contact in both adults and children. Alarmingly the mortality rate seems to be higher, with 4 in 100 cases resulting in death. Mass vaccination in high infection areas is being considered at press.

The disease may become more common since administration of the smallpox vaccine, which confers cross-protection, was discontinued in the 1970s.

What are the signs and symptoms of mpox?

The incubation period from infection to prodromal symptoms of monkeypox is 12 days.

In the first 5 days of the infection, patients experience 'flu-like' symptoms including:

• Fever
• Headache
• Muscle aches
• Back pain
• Malaise (lack of energy)
• Lymphadenopathy (lymph node swelling)
  • The presence of lymphadenopathy is a key sign that differentiates monkeypox from chickenpox.

After this period, a rash similar to that seen in chickenpox develops:

• Lesions predominate on the face but may develop on the palms, soles, and dorsal hands and feet (the latter being unusual in chickenpox)
• Genital and peri-genital lesions have been conspicuous in the recent 2022 outbreak
• Oropharyngeal lesions – erythema, oedema, and ulcers.

The rash begins as 2–5 mm diameter maculopapules, which evolve into:

• Vesicles (small fluid-filled blisters)
• Pseudpustules (solid lesions with an appearance reminiscent of true pustules)
• Crusting over
• Atrophic scars.

Symptoms usually last for 14 to 21 days; the rash lasts for approximately 10 days.

A large series of sufferers from the 2022 outbreak in Spain were reported at the time of writing (August 2022). Many of those affected were men, and had few lesions (less than 20 in total), often only in a single area. Lesions often started on the genitals, face, arms, hands, and perianal area.

Rather than true pustules, pseudo-pustules, which were solid, white, and raised without a top layer that could be scraped off to release pus, were described. Pseudo-pustules are extremely rare in other infections and this is a crucial diagnostic sign. Lesions progressed to small areas of skin necrosis then ulcers; finger lesions produced mpox whitlows. Scarring may occur. Rarely the illness is preceded by a morbilliform eruption.

Suspected mpox

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How is mpox diagnosed?

The prodromal features, coupled with the development of lymphadenopathy, and the chickenpox-like rash should alert suspicion. Unlike chickenpox, lesions may be present on the dorsal hands and feet, palms, and soles.

Virological confirmation can be made by:

• Vesicle fluid or skin exudate electron microscopy
• Viral culture
• Fluid and exudate PCR
• Clade identification by genomic sequencing.

What is the differential diagnosis for mpox?

• Chickenpox
• Smallpox
• Impetigo
• Infected scabies
• Syphilis
• Gonococcal septicaemia
• Lymphogranuloma venereum
• Chancroid
• Granuloma inguinale

What is the treatment for mpox?

With the increased awareness of person-to-person transmission, particularly during the 2022 outbreak, cases should be isolated and contact tracing initiated. Close contacts of infected individuals require isolation for 21 days.

Supportive symptomatic treatment (treatment of secondary infection, pneumonia, and corneal infection) may be needed.

Specific antiviral therapy with cidofovir or a newer agent, tecovirimat may be indicated in those at high risk, or those with severe disease.

Very young patients, malnourished patients, pregnant women, and the immunocompromised may suffer more severe disease.

Smallpox vaccination offers significant protection (85%) against the related monkeypox virus; the risk-benefit of vaccination should be considered for high-risk contacts. Newer two-dose Ankara strain vaccinations have been licensed for prevention of mpox since 2019 in the United Kingdom. It can be administered as post-exposure prophylaxis preferably within 4 days of exposure

Mpox prognosis

In recent years, the mortality of ,pox has ranged from 3–6%, with infants and the immunocompromised having higher mortality.

There were no deaths in the 2003 USA outbreak, and severe illness requiring hospitalisation only occurred in 2 young children.

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Bibliography

• Català A, Clavo Escribano P, Riera J, et al. Monkeypox outbreak in Spain: clinical and epidemiological findings in a prospective cross-sectional study of 185 cases [published online ahead of print, 2022 Aug 2].Br J Dermatol. 2022;10.1111/bjd.21790. doi:10.1111/bjd.21790 Journal
• Maronese CA, Avallone G, Aromolo IF, et al. Mpox: an updated review of dermatological manifestations in the current outbreak.Br J Dermatol. 2023;189(3):260-270. doi:10.1093/bjd/ljad151 Journal
• Moore M, Zahra F. Monkeypox. [Updated 2022 May 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Resource
• 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. doi:10.1371/journal.pntd.0010141. Journal
• Prasad S, Galvan Casas C, et al. A dermatologic assessment of 101 mpox (monkeypox) cases from 13 countries during the 2022 outbreak: Skin lesion morphology, clinical course, and scarring.J Am Acad Dermatol. 2023;88(5):1066-1073. doi:10.1016/j.jaad.2022.12.035 Journal

On DermNet

• Mpox images
• Chickenpox
• Smallpox

Other websites

• CDC Emergency Preparedness and Response — May 20 2022
• Monkeypox — World Health Organisation

Books about skin diseases

• Books about the skin
• Dermatology Made Easy- second edition

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