A new strain of the mpox virus, which has spread from the Democratic Republic of Congo (DRC), is evolving at an alarming rate, raising significant concerns among scientists and public health experts. The strain, known as clade Ib, has mutated faster than anticipated, often in regions where experts lack the necessary funding and equipment to effectively monitor and study the virus. This rapid evolution is making it increasingly difficult to understand the virus’s transmission patterns, severity, and overall impact, according to scientists from Africa, Europe, and the United States.
Mpox, formerly known as monkeypox, has been a persistent public health issue in parts of Africa since the 1970s. However, it gained global attention in 2022 when it surged internationally, prompting the World Health Organisation (WHO) to declare a global health emergency. Although that emergency declaration ended after 10 months, the emergence of clade Ib has once again put the world on high alert. The WHO has declared a new health emergency in response to the strain, which is a mutated version of clade I, historically spread by contact with infected animals in the DRC.
The situation is particularly concerning in Africa, where over 18,000 suspected cases of clade I and clade Ib mpox and 615 deaths have been reported in the DRC alone this year, according to the WHO. Additionally, 222 confirmed clade Ib cases have been reported in four African countries over the past month, along with isolated cases in Sweden and Thailand 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 grave concerns about the current outbreak. “I worry that in Africa, we are working blindly,” he said. Ogoina, who first raised the possibility of sexual transmission of mpox in 2017, now an accepted route of spread for the virus, noted that the rapid mutation of clade Ib is unprecedented, evolving in less than a year compared to the five years it took for clade IIb in Nigeria to develop sustained human transmission, which eventually led to the 2022 global outbreak.
“We don’t understand our outbreak very well, and 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, risk factors of the disease,” Ogoina said. “And I worry about the fact that the virus seems to be mutating and producing new strains.”
Mpox, an orthopoxvirus from the same family as smallpox, has seen population-wide immunity decline since global vaccination efforts ceased after smallpox was eradicated 50 years ago. Genetic sequencing of clade Ib, a strain that emerged around mid-September 2023, reveals it carries the APOBEC3 mutation, indicating the virus is adapting to humans. Typically slow to mutate, mpox’s evolution is now accelerating due to these APOBEC-driven changes, according to Dr. Miguel Paredes from the Fred Hutchinson Cancer Center.
“All human-to-human mpox cases now exhibit this APOBEC mutation, suggesting it’s mutating more rapidly than expected,” Paredes noted. This mutation has complicated response efforts, as multiple mpox outbreaks occur simultaneously.
Historically, mpox spread through human contact with infected animals, which still drives the rise in clade I cases in Congo, largely due to deforestation and increased bushmeat consumption. However, the mutated clades Ib and IIb are now largely considered sexually transmitted diseases, as noted by Dr. Salim Abdool Karim, chair of the Africa CDC’s mpox advisory committee. Clade Ib cases primarily occur among adults, initially spreading among female sex workers in South Kivu, Congo. The virus also spreads through close contact, which explains clusters of infected children in Burundi and eastern Congo’s displacement camps.
Children, pregnant women, and individuals with weakened immune systems are at greater risk of severe disease and death, particularly from clade I, which has a higher fatality rate (4%-11%) compared to clade II (around 1%). Despite the urgency for more research, teams in Africa face significant challenges, such as accessing essential diagnostic chemicals, making it difficult to plan effective responses, including vaccination strategies.
In eastern Congo, where clade Ib is prevalent, about half of cases are diagnosed without laboratory confirmation, according to Dr. Karim. The region’s healthcare system is under severe pressure, exacerbated by ongoing conflicts, and many laboratories lack the necessary supplies to track outbreaks effectively, as highlighted by Dr. Emmanuel Nakoune from the Institut Pasteur in the Central African Republic. He stated that these resources are not a luxury but essential for monitoring and responding to deadly outbreaks.
Melissa Enoch
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