The World Health Organization's chief announced Wednesday he was urgently convening an expert committee to advise on whether the growing mpox outbreak in Africa should be declared an international emergency.
Since last September, cases have surged in the Democratic Republic of Congo due to a strain of the virus which has now been detected in nearby African countries.
WHO chief Tedros Adhanom Ghebreyesus said that given the spread outside the DR Congo, "and the potential for further international spread", he had decided to convene an emergency committee.
"The committee will meet as soon as possible and will be made up of independent experts from a range of relevant disciplines from around the world," he told a press conference.
The committee will advise him on whether the outbreak represents a public health emergency of international concern (PHEIC) -- the highest alarm the WHO can sound.
Only Tedros, as the WHO director-general, can declare a PHEIC, based on the expert committee's advice. A declaration then triggers emergency responses in countries worldwide under the legally binding International Health Regulations.
Formerly known as monkeypox, mpox is an infectious disease caused by a virus transmitted to humans by infected animals but can also be passed from human to human through close physical contact.
The disease causes fever, muscular aches and large boil-like skin lesions.
Tedros said that this year, the DRC had been experiencing a "severe" outbreak of mpox, with more than 14,000 reported cases, and 511 deaths.
While outbreaks have been reported in the DRC for decades, the number of cases in the first six months of this year matched the number registered throughout the whole of 2023.
Furthermore, the virus has spread to previously unaffected provinces in Africa's second-largest country.
"In the past month, about 50 confirmed and more suspected cases have been reported in four countries neighbouring the DRC that have not reported before: Burundi, Kenya, Rwanda and Uganda," Tedros said.
Deadlier virus clade
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Mpox was first discovered in humans in 1970 in the DRC.
There are two subtypes of the virus: the more virulent and deadlier Clade I, endemic in the Congo Basin in central Africa; and Clade II, endemic in West Africa.
In May 2022, mpox infections surged worldwide, mostly affecting gay and bisexual men, due to the Clade IIb subclade.
The outbreak led the WHO to declare a PHEIC, which lasted from July 2022 to May 2023. The outbreak, which has now largely subsided, caused some 140 deaths out of around 90,000 cases.
The cases that have been surging in the DRC since September 2023 are due to a different strain: The Clade Ib subclade.
Tedros explained that this causes more severe diseases than Clade II.
Rosamund Lewis, the WHO's technical lead for mpox, said the case fatality rate overall in the DRC was around 3.6 per cent.
However, it is "higher in endemic areas, and especially in infants and young children, and lower in the eastern part of the country at the moment, where spread is more rapid through sexual transmission", she added.
Clade Ib has been confirmed in Kenya, Rwanda and Uganda, while the clade in the Burundi cases is still being analysed.
Two vaccines for mpox are recommended by the WHO's immunisation experts.
A PHEIC has only been declared seven times since 2009: over H1N1 swine flu, poliovirus, Ebola, Zika virus, Ebola again, Covid-19 and mpox.