Mpox disease is caused by a virus of the same name and is a member of the Orthopoxvirus genus in the family Poxviridae. It was first identified in Denmark in 1958, when an outbreak of a pox-like disease broke out in a colony of macaques being kept for research, and identified in humans in 1970. It has since circulated increasingly in human populations in endemic areas of Central and West Africa. In these areas, infection spreads between wild animal species and humans. The exact animal reservoir of infection remains unknown, although various animal species are known to be susceptible to the virus, including a range of rodents and primates. Normally, monkeypox is not easily transmitted between people as it requires very close physical contact to allow the virus to be able to enter the body. There are two distinct types of monkeypox: the Congo Basin (Central African) clade, which can potentially cause more serious disease, and the West African clade, which tends to cause milder disease. The disease is usually self-limiting, with most of those infected recovering within a few weeks without the need for treatment. However, the disease can be more severe, especially in young children, pregnant women, and individuals who are immunocompromised.