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Author: Marika Gilbourne, Medical Student, Nottingham University, England; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand; Copy Editor: Clare Morrison, 2 May 2014.
Monkeypox is a rare disease caused by the monkeypox virus (also known as MPV). The monkeypox virus has the genus Orthopoxvirus – the same family of viruses as cowpox and smallpox. Infection with the MPV virus causes a skin 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.
Monkeypox is spread through animal-to-human transmission, which means that it only occurs in people who have been in contact with an animal carrying the disease. The animal could be a monkey, mouse, rope/tree squirrel or a Gambian rat. Outbreaks of monkeypox have been confined to the tropical rainforests of central and western Africa, particularly in the Democratic Republic of Congo. However, more recently there have been outbreaks of the disease in the USA and Sudan. The risk of human-to-human transmission of the virus is low, but has been documented in people who have had very close contact with an infected individual.
In the first 5 days of manifestation of the infection, patients experience 'flu-like symptoms including:
Note: The presence of lymphadenopathy is the key symptom which differentiates monkeypox from chickenpox.
It can take up to 12 days for these 'flu-like symptoms of monkeypox to develop from the initial exposure to the virus. These symptoms usually last 14 to 21 days.
After this period, a rash, similar to that seen in chickenpox, develops; predominantly on the face, but possibly also occurring on the palms and soles. The rash appears as maculopapules (lesions with a flat base) 2–5 mm in diameter, which change to vesicles (small fluid-filled blisters) and then crust over. The rash usually lasts approximately 10 days or more.
The monkeypox rash can look similar to that of smallpox, chickenpox, syphilis, measles, scabies and some bacterial skin infections/impetigo. For this reason, a definite diagnosis of monkeypox cannot be based on clinical findings alone.
Blood samples, viral swabs and skin samples need to be sent to the laboratory for diagnostic testing. The United States Center for Disease Control (CDC) has published guidance for safe sample collection to minimise risk of infection to health workers (see references below)
There are no specific treatments or vaccinations currently available for monkeypox. A broad spectrum antiviral agent, such as cidofovir, can be used in very severe cases but its efficacy is unknown.
Due to the similarities of the viral agents that cause monkeypox and smallpox, the vaccination for smallpox has been used and has been 85% effective at preventing the disease. People who contracted monkeypox after having had smallpox vaccination contracted a significantly milder form of monkeypox. All health workers or people in close contact with someone infected with monkeypox are advised to be vaccinated.
As with chickenpox, children are more likely to suffer from monkeypox than adults; most fully recover after 21 days without scarring of the skin. Monkeypox has the potential to cause death, especially in young children; 10% of those who contracted the disease in Africa died. However, there were no deaths in the outbreak in the USA in 2003, and severe illness, requiring hospitalisation, only occurred in 2 young children.
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