Mpox is back – and in new countries. How can this outbreak be contained?

The public health emergencies in 2022 and 2024 saw the virus reported in 145 countries, but in the new cases children appear particularly affected

A fresh outbreak of mpox in Guinea Bissau – the country’s first – means the virus formerly known as monkey pox is back in the headlines. So what has changed?

Since 2022, there have been almost 190,000 lab-confirmed cases of mpox reported worldwide in 145 countries. Before then, outbreaks of mpox tended to be relatively small and in a handful of African countries, where the viral infection was known to be endemic.

It used to be called monkeypox, because the virus was first discovered in captive monkeys in 1958. But during an international outbreak in 2022, there were concerns that the name was fuelling racist and stigmatising language on and offline, prompting the World Health Organization (WHO) to recommend changing it to mpox .

It is endemic to many parts of Africa, with outbreaks historically starting when people ate meat from infected wild animals. But in recent years it has spread beyond the usual areas, with sustained chains of human-to-human transmission. The Atlanta-based Centers for Disease Control and Prevention said this month that mpox was on course to become endemic in the US .

There are, broadly, two types of mpox, known as “clades”. Clade I was once called the “Congo Basin clade” and clade II the “West African clade”.

The latter sparked a major global outbreak in 2022 when it appeared to undergo some changes that allowed it to spread more efficiently from person to person. It is passed on via close contact – in that outbreak, mostly by sexual contact, with men who have sex with men at the highest risk .

In June 2024, researchers raised the alarm about a new variant of clade I in the Democratic Republic of the Congo (DRC), which also appeared to be spreading more easily between people. That grew into another major international outbreak, which was declared a public health emergency of international concern by the WHO on 14 August 2024.

“Emergence of mpox in more countries in west Africa is to be expected,” said Prof Michael Marks, of the London School of Hygiene & Tropical Medicine and University College London hospital. “Mpox outbreaks have now been declared in a number of countries in the region, including Guinea and Sierra Leone within the last 12 months.

“Mpox spreads by close physical contact. This makes it suitable to spread in a variety of different contexts, such as in close sexual networks, as was seen during the 2022 global pandemic, or areas where many people are living closely together such as settings with refugees and internally displaced people, as was seen in the DRC outbreak over the last few years,” Marks said.

The 2022 outbreak was declared a public health emergency in July that year. After contact-tracing and mass vaccination programmes, the status was lifted in May 2023.