Scientists studying a new strain of mpox, which has spread from the Democratic Republic of Congo, say the virus is mutating faster than anticipated. They note that many areas lack the necessary funding and equipment to track these changes effectively.
This presents significant challenges regarding the virus’s characteristics, severity and transmission, complicating the response, according to several scientists in Africa, Europe and the U.S.
Mpox, previously known as monkeypox, has been a public health issue in parts of Africa since 1970 but garnered global attention only when it surged internationally in 2022. The World Health Organization (WHO) declared a global health emergency at that time, which ended 10 months later.
A new strain, clade Ib, has refocused global attention after the WHO declared another health emergency. This strain is a mutated version of clade I, which has been endemic in Congo for decades. Mpox typically causes flu-like symptoms and pus-filled lesions and can be fatal.
The WHO reports over 18,000 suspected cases of clade I and clade Ib in Congo this year, with 615 deaths. There have also been 222 confirmed clade Ib cases in four African countries recently, and isolated cases in Sweden and Thailand have been linked to travel in Africa.
Dr. Dimie Ogoina, an infectious disease expert at Niger Delta University Hospital in Nigeria and chair of the WHO’s mpox emergency committee, expressed concerns about the lack of understanding and resources in Africa. He highlighted that the virus is mutating rapidly, complicating outbreak management.
Ogoina noted that clade IIb in Nigeria took over five years to evolve enough for sustained human transmission, leading to the 2022 outbreak. In contrast, clade Ib has evolved similarly in less than a year.
Mutating ‘more rapidly’
Mpox, an orthopoxvirus related to smallpox, has seen reduced global immunity due to the cessation of smallpox vaccination after the disease was eradicated. Clade Ib, emerging around Sept. 2023, carries the APOBEC3 mutation, accelerating viral evolution.
Dr. Miguel Paredes of Fred Hutchison Cancer Center in Seattle explained that all human-to-human mpox cases exhibit this mutation, indicating faster-than-expected viral changes.
The response is further complicated by concurrent outbreaks. Traditionally, mpox spread through human contact with infected animals. However, clade Ib and IIb have transitioned to being sexually transmitted diseases, with most cases in adults, initially driven by an outbreak among female sex workers in South Kivu, Congo.
The virus can also spread through close contact, which is likely how clusters of children have contracted clade Ib, particularly in displacement camps with overcrowded conditions.
Children, pregnant women and those with weakened immune systems face higher risks of severe disease and death, according to the WHO.
Clade I typically causes more severe disease, with a fatality rate of 4%-11%, compared to about 1% for clade II. While Congo data indicates few deaths from clade Ib, there are concerns about data accuracy.
Urgent research is needed, but teams tracking outbreaks in Africa report a lack of necessary diagnostic chemicals and limited access to labs. About half of cases in eastern Congo, where clade Ib is prevalent, are diagnosed by doctors without laboratory confirmation.
Dr. Emmanuel Nakoune of Institut Pasteur in Bangui, Central African Republic, emphasized the necessity of tracking outbreaks, noting that many African labs lack essential supplies.
