Mpox, formerly known as monkeypox, has been a public health concern in parts of Africa since the 1970s. Despite its long history, it gained little international attention until a surge in cases in 2022 prompted the World Health Organization (WHO) to declare a global health emergency—a status that was lifted ten months later. However, the emergence of a new strain, clade Ib, has reignited global concern, leading the WHO to declare another health emergency.
Clade Ib is a mutated version of clade I, a form of mpox endemic to Congo that typically spreads through contact with infected animals. This year, Congo has reported over 18,000 suspected cases of clade I and Ib mpox, resulting in 615 deaths, according to the WHO. Additionally, 222 confirmed clade Ib cases have been identified in four African countries over the past month, along with individual cases in Sweden and Thailand linked to travel from Africa.
Mpox is part of the orthopoxvirus family, which includes smallpox. The global vaccination efforts from fifty years ago have diminished, as routine vaccinations ceased after smallpox eradication. Genetic sequencing of clade Ib infections, which emerged around mid-September 2023, reveals a mutation known as APOBEC3. According to Dr. Miguel Paredes of the Fred Hutchinson Cancer Centre in Seattle, this mutation signifies the virus’s adaptation to humans and accelerates its evolution.
Traditionally, mpox transmission was primarily through human contact with infected animals, a trend still evident in Congo due to factors like deforestation and increased bushmeat consumption. However, the mutated clade Ib and IIb strains are now effectively classified as sexually transmitted infections. Dr Salim Abdool Karim, a South African epidemiologist and chair of the Africa CDC’s pox advisory committee, explains that most clade Ib cases occur among adults, initially driven by an outbreak among female sex workers in South Kivu, Congo. The virus also spreads through close personal contact, leading to clusters of infections among children in Burundi and displacement camps in eastern Congo, where crowded living conditions facilitate transmission.
Vulnerable populations, including children, pregnant women, and individuals with weakened immune systems, face a higher risk of severe mpox disease and death, the WHO warns. While clade I has been associated with higher fatality rates of 4–11%, clade II is around 1%. Preliminary data from Congo suggest that the new clade Ib may have a lower fatality rate, although concerns about potential data misclassification exist.
According to three teams tracking mpox outbreaks in Africa, research efforts on the evolving virus are hindered by a lack of essential chemicals for diagnostic tests. Without these resources, developing effective response strategies, including vaccination plans, is extremely challenging.
In a related development, Danish biotech company Bavarian Nordic announced on Tuesday that its mpox vaccine, Jynneos, has been approved by Singapore’s medicines regulatory authority. The vaccine is authorized to prevent smallpox and mpox in individuals aged 18 or older who are considered high-risk, marking full approval for Jynneos in Singapore.