What is mpox, and why did WHO declare it a global emergency twice?

Mpox is a viral disease, usually mild, that mainly causes a rash of blisters that crust over, with fever and swollen lymph nodes. Most people recover within a few weeks without treatment, although cases may be severe, especially in children, pregnant women or people with suppressed immune systems. It is caused by a virus from the same genus as the one behind smallpox, and it is zoonotic: it lives in animals and sometimes jumps to people. Between people it spreads through direct contact with infected skin or body fluids.

The World Health Organization (WHO) has declared mpox a global emergency twice. The first time was on 23 July 2022, when a clade IIb outbreak spread to many countries; the first case had been detected in London on 6 May 2022 in a patient who had traveled from Nigeria. It was the first widespread community transmission outside Africa, and the WHO ended the emergency on 11 May 2023. The second was on 14 August 2024, for clade Ib, a new variant of clade I first detected in the Democratic Republic of the Congo in 2023 and by then spreading in parts of Africa. The WHO announced it was over on 5 September 2025, citing sustained declines in cases and deaths in the Democratic Republic of the Congo and other affected countries.

Mpox has also changed names. It was found in 1958 in research monkeys, hence "monkeypox", but there is little evidence that monkeys are a reservoir. Squirrels are suspected in Central and Western Africa, and in November 2022 the WHO announced the new name "mpox". Public health experts had urged a rename to decrease association with Africa.