Mpox is caused by the monkeypox virus (MPXV), an enveloped double-stranded DNA virus. It is a member of the Orthopoxvirus genus in the family Poxviridae. There are two distinct clades of the virus: clade I (Central African/ Congo Basin) (subclades Ia and Ib) and clade II (West African) (subclades IIa and IIb). Clade I infections are generally more severe and more transmissible, with higher mortality rates, while Clade II infections are typically milder and were responsible for the 2022–2023 global outbreak and continues to circulate internationally. 

Mpox can be transmitted through close contact with an individual who has mpox, with contaminated materials, or with infected animals. The virus can spread between people through skin-to-skin contact with sores, scabs, respiratory droplets or oral fluids, usually through close, intimate situations. Most of the recent spike in cases has been through sexual transmission. Infection is also transmitted through contact with animals, such as via infected rodents through broken skin (bites or scratches), or direct contact with an infected animal’s blood, bodily fluids or pox lesions (sores). 

Incubation period is 5-13 days, although it can take up to 21 days. Early symptoms include fever, headache, muscle ache, backache, swollen lymph nodes, chills and exhaustion, followed by a rash on the face, hands and feet, that can spread to the inside of the mouth, the genitals and the cornea. The rash can last 2–4 weeks.  With no specific antiviral treatment available, treatment of Mpox is mainly symptomatic.

Mpox was first discovered in 1958 when outbreaks of a disease that caused pox-like symptoms were discovered in monkeys held in captivity for research. It was first seen in humans in 1970 in the Democratic Republic of the Congo (DRC) and it is now endemic in Central and West Africa. The geographic range of mpox is mostly West and Central Africa. 

In 2017, Nigeria saw a re-emergence of cases after nearly four decades of zero cases; and the disease was spreading in an unusual way. Most patients were young men who had lesions or skin rashes and ulcers around the genital area, which suggested that mpox might also be spread through sexual contact. By this point, DRC had also seen cases steadily rising. A global outbreak of clade IIb began in 2022 and continues to this day, including in some African countries. There are also growing outbreaks of clades Ia and Ib affecting the DRC and other countries in Africa. As of 2024, clade Ib has also been detected beyond Africa. 

In May 2022, a case of mpox was detected in the UK, and soon several more, apparently unconnected cases, were found, spreading across borders in Europe and to the US. It soon emerged that most of the cases across Europe and the US were in men who have sex with men, especially those who had closely connected sexual networks, allowing the virus to spread in a different way than in the general population. By July 2022, WHO declared the global outbreak a Public Health Emergency of International Concern (PHEIC). The 2022–2023 global outbreak was caused by the clade IIb mpox strain

Just over a year later, on 14 August 2024, WHO declared once more that mpox was a PHEIC. This declaration was prompted by a surge of mpox cases in countries like DRC, and also in neighbouring countries that had never seen mpox before, such as Burundi, Kenya, Rwanda and Uganda. This was caused by the more deadly clade I strain. 

In 2025, it was reported to WHO that between January–May 2025, 24,672 confirmed cases and 82 deaths were reported across 75 countries. Most cases were in Africa, especially Central and East Africa. Outside Africa, smaller clusters continue in Europe, North America, Asia, and Latin America, mostly linked to Clade II.