Monkeypox infection is a viral zoonotic (animal to human transmission) disease caused by the monkeypox virus which is part of the Orthopoxvirus genus of viruses, which includes smallpox (variola virus). The monkeypox virus was first identified in 1958 in monkeys, which is how the name was derived, and the first case in people was recorded in 1970 in the Democratic Republic of the Congo during the smallpox eradication efforts.
Historical genetic testing has shown that the monkeypox virus mutates slowly over time and having received a smallpox vaccination within the prior 3 years is estimated to be 85% effective in preventing monkeypox infection. However global vaccination for smallpox stopped in the 1970s when smallpox was eradicated globally. Since the 1990s the number of monkeypox cases has steadily increased as detection has improved. Global travel has increased the spread of diseases, children are no longer being vaccinated for smallpox, and adults experience waning immunity over time.
As of May 24, 2022 there is currently an outbreak of Monkeypox with 250 confirmed and suspected cases reported in 16 countries including the regions of North America, Europe, and Australia. Approximately 1/3 of infected people required hospitalization, suggesting there are more cases where people have milder symptoms and have not sought medical care.
The natural reservoir is not established but believed to involve rodents. However, efforts to find the virus in rodents and other animals have only rarely found the virus. It is possible there is another yet to be identified reservoir that is the primary reservoir, but the reservoir is not believed to be people.
The symptoms of monkeypox infection are similar to those of smallpox (but generally milder), making it difficult to distinguish between the two initially. Only a trained physician should attempt to diagnose monkeypox infections as this initial presentation of signs and symptoms can be very similar to other infections and a physician can arrange for testing to conclusively diagnose monkeypox infection.
The monkeypox virus can enter the body through broken skin, the respiratory tract, or mucous membranes. The virus is not believed to be easily passed from person to person since a large dose of virus is believed to be needed to cause transmission to another person.
The incubation period is typically 6-13 days, but can range from 5-21 days, so a significant amount of time can pass between exposure and the first signs or symptoms. In general, pox viruses are not likely to be transmitted between people until signs or symptoms occur, so asymptomatic transmission is not believed to be likely.
Initial symptoms include:
Typically 1-3 days after the onset of fever, the infected person develops a rash on the face, palms of hands, and bottom of feet. Other areas of the body can develop rash over time. Pustules/lesions from the rash contain fluid with high concentrations of virus and are believed to be the main source of subsequent person to person transmission.
The main initial difference between monkeypox and smallpox infection is that monkeypox causes the lymph nodes to swell, while smallpox does not. Within 1-3 days of the start of fever, people infected with monkeypox usually develop a rash often beginning on the face and then spreading to other parts of the body, during which time lesions develop, scab, and fall off. The infection typically lasts 2-4 weeks and has a 1-10% mortality rate. Prompt medical care can significantly reduce the risk of mortality as there are highly effective therapeutics available. Hospitalization is more likely in children than adults.
There is a new vaccine that helps prevent monkeypox infections, but it is not widely distributed currently. As mentioned above, prior smallpox vaccination provides some measure of protection in preventing monkeypox infection as well for those vaccinated prior to 1980, although immunity has likely waned over time.
The primary methods of prevention include:
For more information, these websites are good sources for information and were used to prepare this document.
World Health Organization: https://www.who.int/news-room/fact-sheets/detail/monkeypox
US-Centers for Disease Control and Prevention: https://www.cdc.gov/poxvirus/monkeypox/index.html
*Please follow country regulations to determine what is appropriate at the local level.