The Virus That Causes Monkeypox (Mpox) Keeps Getting Better at Spreading in People
A recent analysis of a strain of the virus causing Mpox suggests that it may be rapidly spreading from person to person. This development, primarily observed in Central Africa, poses a significant challenge to efforts to contain the disease, which has seen a surge in infections over the past year. Researchers are puzzled by the factors driving this surge and are working diligently to understand the evolving nature of the virus.
The strain in question, known as clade Ia, appears to be spreading sustainably between individuals, possibly through sexual contact, in an outbreak in Kinshasa, the capital of the Democratic Republic of the Congo (DRC). Previously, this particular variant was mostly transmitted from animals to humans in Central Africa.
Placide Mbala, head of epidemiology and global health at the National Institute of Biomedical Research in Kinshasa, who co-led the analysis, commented on the findings, stating, “We know that viruses evolve – we have seen it with Ebola, we have seen it with COVID, and we expected to see it with Mpox as well. We don’t know how far these adaptations can go, and we are gathering data to understand how this evolution is occurring.”
The preliminary results of this study, although not yet peer-reviewed, were shared on October 22 on the genomic-epidemiology discussion forum Virological.
Mpox has four known variants: clades Ia, Ib, IIa, and IIb. Historically, clade I viruses have been prevalent in Central Africa, while clade II viruses have been more common in West Africa. However, a shift occurred in the mid-2010s when a clade II strain triggered an outbreak in Nigeria, raising concerns about potential transmission through sexual contact. This hypothesis was confirmed when a similar clade II strain, IIb, led to a global Mpox outbreak in 2022, infecting over 90,000 individuals.
In late 2023, researchers identified a rapidly growing outbreak of a clade I virus in densely populated urban areas of the DRC. This particular strain, named Ib, exhibited significant genetic differences from other clade I viruses and demonstrated the ability to spread between individuals. The outbreak caused by clade Ib has since spread to various countries worldwide, resulting in thousands of infections and fatalities in the DRC.
Now, approximately a year after the outbreak of clade Ib, clade Ia is causing concern among health officials. This strain is on the rise in western regions of the DRC and Kinshasa, posing a significant threat to the city’s 17 million residents and increasing the likelihood of international spread due to Kinshasa’s status as a travel hub.
Researchers have utilized genomic sequencing to track the outbreak and have observed distinct genetic mutations in virus samples from infections in Kinshasa, indicating sustained human-to-human transmission. This pattern was not present in earlier studies, suggesting that it may be a recent development, highlighting the evolving nature of the virus causing Mpox. In rural and endemic regions of the Democratic Republic of the Congo (DRC), researchers have not observed strong signs of evolution in the mpox virus, according to virologist Jason Kindrachuk from the University of Manitoba. However, a unique trend has been noted in the capital city of Kinshasa. Clade Ia, a specific strain of the virus, has shown potential for transmission through sexual contact. Recent reports have described the first probable case of sexually transmitted clade I mpox, with more studies on this phenomenon forthcoming.
The presence of clade I in both animals and humans in the DRC since 1970 raises questions about the sudden emergence of clade Ib in 2023 and the increase in infections attributed to clade Ia in recent years. Kindrachuk emphasizes the importance of investigating factors such as improved surveillance, heightened community awareness of mpox, increased human mobility post-COVID-19 pandemic, and enhanced contact with wildlife that may contribute to these trends.
Despite these developments, plans to introduce the first mpox vaccines in Africa are expected to proceed as scheduled. Nicaise Ndembi, a virologist at the Africa Centres for Disease Control and Prevention, explains that vaccine distribution will prioritize regions with higher infection rates regardless of the specific viral strain present.
As the scientific community continues to monitor and analyze the evolution and transmission patterns of the mpox virus in the DRC, ongoing research and surveillance efforts will be crucial in informing public health strategies and interventions. The original article was published on October 30, 2024, and further updates on this topic are anticipated as new data becomes available.
