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Monkeypox

Authors: Marika Gilbourne, Nottingham University, England; Chief Editor: Dr Amanda Oakley, Dermatologist, New Zealand; updated by Dr Ian Coulson, Dermatologist, UK. Copy edited by Gus Mitchell. May 2022


Monkeypox — codes and concepts
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What is monkeypox?

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

Monkeypox 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. 

Who gets monkeypox?

There are two principal clades (strains) of the monkeypox virus that produce sporadic outbreaks in Africa (numbering 1 to 2 thousand cases a year); a more virulent clade in the Congo basin and a milder clade 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.

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

As of mid June 2022, the majority of cases (87%) are from the European region (approx. 1100 cases) followed by the Americas (approx. 150), Eastern Mediterranean Region (14), and Western Pacific Region (6). Person-to-person spread is evident from close physical proximity or sexual activity, predominantly in men who have sex with men; none had recent African travel. So far all cases have been linked to the less virulent West African strain.

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 monkeypox?

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.

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

  • Vesicles (small fluid-filled blisters)
  • Pustules
  • Then crust over. 

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

Suspected monkeypox

How is monkeypox 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 monkeypox?

What is the treatment for monkeypox?

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 licenced for prevention of monkeypox since 2019 in the United Kingdom. 

Monkeypox prognosis

In recent years, the mortality of monkeypox 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.

 

Bibliography

  • 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

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