"Mpox is not the new Covid," said Hans Kluge, director of the European branch of the World Health Organization (WHO), on Tuesday, August 20. This is despite the fact that a week earlier, the UN organization had declared a public health emergency of international concern (PHEIC) for the disease which, since the beginning of the year, has caused almost 19,000 cases and 541 deaths on the African continent. Here are the answers to the main questions raised by this disease, which is endemic in many African countries.

None, it's the same disease. On November 28, 2022, WHO decided to change the official name of monkeypox. This decision, unusual in the midst of an epidemic outbreak, was taken in reaction to "racist and stigmatizing remarks" aimed at sufferers, mainly among the African population and the homosexual community.

The virus has kept the name "monkeypox virus." It derives from the conditions in which it was first identified: in 1958, in Copenhagen, Denmark, in a colony of monkeys imported for research and showing smallpox-like symptoms. The first human case was not detected until much later, in 1970 in the Democratic Republic of Congo (DRC), in a 9-month-old child.

Since then, research has shown that the main animal reservoir – in other words, the species among which the virus circulates in the wild – is rodents, in particular tree squirrels, although monkeys can also be contaminated.

The term "pox" refers to smallpox, which belongs to the same family of rash-causing pathogens known as orthopoxviruses. There is a strong cross-immunity between the different members of this small family, meaning that an infection caused by one offers good protection against the others. This is why health authorities recommend the use of vaccines originally developed for smallpox, such as the Bavarian Nordic vaccine, to combat mpox. This is produced from another orthopoxvirus cousin: vaccinia, a virus affecting cows (vacca in Latin), which has gone down in history as giving its name to vaccination.

Four viruses causing mpox disease are currently in circulation. Specialists refer to these as "clades," not "variants." These terms do not refer to the same degree of genetic proximity.

Currently, clade 1 has been identified in the Congo Basin, in other words in the DRC, Central African Republic (CAR) and Republic of the Congo. Subclade 1a has been endemic there since the 1970s, while subclade 1b emerged in September 2023 in the eastern DRC, in South Kivu. It is the emergence and spread of subclade 1b in neighboring countries that is worrying international organizations. Clade 2 is mostly found in West Africa (Nigeria, Benin, Ghana and Liberia), but also in the south (South Africa and Mozambique) and the north (Egypt and Sudan). Subclade 2b diverged from subclade 2a from 2017 onward and spread extensively outside Africa in 2022-2023.

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