Just over a year after the last mpox outbreak was deemed to no longer be a global emergency, the World Health Organization (WHO) has once again sounded its highest alarm, declaring Central Africa鈥檚 mpox surge a public health emergency of international concern (PHEIC).
Mpox, formerly known as monkeypox, was made a PHEIC for the first time in July 2022 as it spread rapidly across a range of countries where it hadn鈥檛 been reported before.
Despite that emergency ending in May 2023, reported infections went on to increase significantly and the number tallied so far this year already exceeds 2023鈥檚 total, . The virus has also spread beyond its endemic countries in Central and West Africa, with cases being reported in Kenya, Rwanda, Burundi and Uganda for the first time.
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So, why are we in this situation? How is mpox a global emergency again so soon after the last one? To answer these questions, we need to look back to the WHO鈥檚 first mpox PHEIC announcement, which came after cases were reported outside of endemic regions of Africa, including in the UK, US and Australia. This in turn led to these countries ramping up access to smallpox vaccines that work against the related mpox virus, which were targeted to those most at risk, including men who have sex with men.
These efforts helped cases to subside in these parts of the world. But in the DRC, where mpox was first identified in humans in 1970, vaccines were largely unavailable. This was due to a lack of funding and other countries not donating them, allowing the outbreak to persist, says at the University of Oxford.
This meant the virus could spread, mutate and evolve, which resulted in the emergence of a new version, or clade, of mpox.
There are two main types of mpox: clade I and clade II. While these both circulate in Central and West Africa, a subtype of clade II drove the global outbreak in 2022, while the ongoing surge is due to a subtype of clade I, called clade Ib. This may have emerged even if vaccination efforts had been better, says , also at the University of Oxford. 鈥淭hese things will pop up,鈥� she says.
But widespread vaccination in endemic countries would undoubtedly have helped control clade I, reducing the risk of it evolving. 鈥淭here鈥檚 no doubt that if we had more vaccines, there鈥檇 be less clade I,鈥� says Lang.
鈥淚t鈥檚 always hard to say what 鈥榳ould鈥� happen, but mutations are a numbers game,鈥� says at Columbia University in New York. 鈥淭he more infections you have, the greater the chance of a meaningful mutation. If we were able to vaccinate more people in the DRC over the past one to two years, it鈥檚 likely we would have seen less cases, less spread, and I suspect not ended up with another public health emergency of international concern.鈥�
Along with more research and surveillance, adequate vaccination would have meant that the 鈥渃hances are we wouldn鈥檛 be here today鈥�, says Olliaro.
, with clade I being more severe than clade II. A lack of research makes it hard to say whether clade Ib differs to previous clade I subtypes in terms of severity and transmission, but it is thought to largely spread via sex and other forms of close contact, as we saw in the 2022 outbreak.
Despite the unknowns, it is clear that the outbreak has an increasing chance of spreading, both in the regions surrounding Central and West Africa and beyond, says Zucker. The declaration of a PHEIC is therefore considered by the experts to be a wise move. 鈥淓verybody鈥檚 very pleased that [the PHEIC] was made because it mobilises the vaccine response and coordinated effort that we need,鈥� says Lang.
To prevent a third mpox PHEIC, the focus must pivot to endemic countries in Central and West Africa. They have been 鈥渇acing this problem for years鈥�, says Olliaro. 鈥淎fter the end of the last PHIEC, the alarm went off but we went back to sleep.鈥� It鈥檚 time to wake up, he says.
