Mpox (previously known as monkeypox) is a viral disease caused by an orthopoxvirus called monkeypox virus. It spreads mainly through close contact with someone who has mpox, causing a painful rash, enlarged lymph nodes and fever. It can make people very sick and leave scars.

The disease mainly spreads from person to person through close contact. This includes, but isn’t limited to, sexual contact. Transmission occurs through exposure to bodily fluids; lesions on the skin or on internal mucosal surfaces, such as in the mouth or throat; respiratory particles; and contaminated objects. 

In areas where animals carry the virus, mpox is a zoonotic disease, meaning it can spread from animals to humans. It's found in tropical rainforests in central, east and west Africa, where small mammals such as squirrels, Gambian pouched rats, dormice, and various species of monkeys may be carriers.

Since May 2022, mpox has spread globally, with cases reported from countries without previously documented mpox transmission. The spread in most countries today is from people and not animals.

Mpox typically causes a fever, a rash resembling pimples or blisters and swollen lymph nodes.   Symptoms usually appear within a week of exposure but can take anywhere from 1 to 21 days to develop.

The illness often begins with a feverish phase lasting 1 to 3 days with symptoms including intense headache, swollen lymph nodes back pain, muscle aches and severe fatigue. The first stage is followed by the skin eruption stage, lasting from 2 to 4 weeks. Lesions evolve from macules (lesions with a flat base) to papules (raised firm painful lesions) to vesicles (filled with clear fluid) to pustules (filled with pus), followed by scabs or crusts.  They can leave scars. For some people, the first symptom of mpox is the rash.

Some people with mpox become very sick and it can even be fatal in some cases. Children, pregnant people and people with weak immune systems, including people living with HIV that is not well controlled, are at higher risk for serious illness and death due to complications from mpox.

Prevention and control of mpox rely on raising awareness in communities and educating health workers to prevent infection and stop transmission.

Mpox vaccines also provide protection against infection and severe disease. WHO recommends the use of vaccines for those most at risk of exposure during outbreaks, including people who have had close contact with someone with mpox, and health workers. People who were vaccinated against smallpox in childhood may have some cross-protection against mpox. 

To prevent spread, close contact with people who have mpox or with contaminated materials should be avoided. Masks, gloves and other personal protective equipment should be worn while taking care of the sick, whether in a health facility or at home. 

Where animal-to-human transmission is possible, contact with sick or dead animals should be avoided, and all foods containing animal meat or parts must be properly cooked before consumption. 

Care of patients with mpox should focus on managing symptoms to make people feel better, and to prevent medical complications. Potential treatments against mpox are being developed and tested.