A new strain of the mpox virus, clade Ib, is rapidly spreading out of the Democratic Republic of Congo, raising concerns among scientists. The strain has evolved faster than expected and its transmission dynamics remain unclear. This new development has prompted the World Health Organization (WHO) to declare a new health emergency, drawing global attention to the mpox outbreak.
The mpox virus typically causes flu-like symptoms and pus-filled lesions, and it can be fatal. While the virus has been a public health concern in parts of Africa since 1970, a resurgence in 2022 led the WHO to declare a global health emergency, which was later lifted. However, the emergence of clade Ib, a mutated version of the endemic clade I, has reignited anxieties.
Congo has reported over 18,000 suspected cases of clade I and clade Ib mpox and 615 deaths this year, according to the WHO. In recent weeks, 222 confirmed clade Ib cases have been identified in four African countries, with isolated cases also reported in Sweden and Thailand, linked to travel from Africa.
Scientists from Africa, Europe, and the United States have expressed deep concern over the lack of information surrounding the virus, including its severity and transmission dynamics. Dr Dimie Ogoina, an infectious disease expert in Nigeria and chair of the WHO’s mpox emergency committee, highlighted the limited understanding of the outbreak. “We don’t understand our outbreak very well,” Ogoina said. “If we don’t understand our outbreak very well, we will have difficulty addressing the problem in terms of transmission dynamics, the severity of the disease, [and] risk factors.”
Ogoina pointed out that while it took clade IIb in Nigeria over five years to evolve enough to sustain human-to-human transmission, triggering the 2022 global outbreak, clade Ib has achieved similar capabilities in less than a year. Mpox, an orthopoxvirus related to smallpox, has historically been slow to mutate. However, genetic sequencing of clade Ib infections, which the WHO estimates emerged in mid-September 2023, revealed a mutation known as APOBEC3, indicating the virus’s adaptation to human hosts. This mutation is accelerating viral evolution, according to Dr Miguel Paredes from Fred Hutchinson Cancer Center in Seattle.
Paredes underscored the complexity of the situation, with several simultaneous mpox outbreaks unfolding. While previously mpox was primarily spread through human contact with infected animals, the mutated versions, clade Ib and IIb, are now largely considered sexually transmitted diseases. The virus has also spread through close contact, contributing to clusters of infections among children in Burundi and in eastern Congo’s displacement camps, where crowded living conditions may exacerbate the spread.
Urgent research is crucial, but African scientists are facing challenges in accessing essential chemicals and equipment for diagnostic tests. This limitation hampers effective planning and implementation of a response, including vaccination strategies. Many African laboratories are facing shortages of necessary supplies, said Dr Emmanuel Nakoune of the Institut Pasteur in the Central African Republic. “This is not a luxury,” Nakoune stressed. “It is necessary to track deadly outbreaks.”
