Mpox Outbreak Update: New Strain, Clade Ib, Drives Surge in Cases Across Africa

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Mpox, a viral illness first identified in Africa in 1970, has re-emerged in recent years as a global health concern. The outbreak, which made headlines in 2022 due to its rapid spread across the globe, has evolved significantly, with multiple strains now circulating in different countries. The most recent surge in mpox cases is largely attributed to a new strain, known as clade Ib, first discovered in the Democratic Republic of the Congo (DRC).

New Strain Raises Concerns

Clade Ib is currently responsible for much of the rise in mpox cases. According to the World Health Organization (WHO), clade Ib has spread beyond the DRC to neighboring countries, including Burundi, Rwanda, Uganda, and Kenya, as well as more distant locations like Sweden and Thailand, where one case each has been identified. The DRC, however, remains the epicenter of the outbreak, accounting for about 90% of mpox cases in the African region.

Dr. Fiona Braka, the Emergency Response Manager for WHO’s African region (AFRO), stated that the DRC is experiencing two distinct outbreaks. Clade Ia is circulating in regions where mpox is considered endemic and primarily affects children. In contrast, clade Ib is spreading mostly among adults in the eastern provinces of South Kivu and North Kivu.

Braka emphasized that the situation remains complex, with many unknowns due to limited diagnostic and testing capabilities in affected areas, which hinder a full understanding of the true burden of disease.

Genetic Differences and Multiple Outbreaks

During a special session on the mpox outbreak at the WHO Regional Committee for Africa meeting in late August, experts highlighted the complexity of the current situation. Dr. Jean Kaseya, Director-General of the African Centre for Disease Control (CDC), remarked, “We don’t have one outbreak. We have multiple outbreaks in one.” This is due to the different clades of the mpox virus circulating, each with unique genetic mutations.

Professor Tulio de Oliveira, Director of the Centre for Epidemic Response and Innovation (CERI) at Stellenbosch University, explained that these genetic differences define the virus’s clades, similar to how variants of SARS-CoV-2, the virus causing COVID-19, are classified.

Clade Ib, which emerged as a sub-clade of clade I in the DRC, has raised concerns due to its possible increased severity, particularly in immunocompromised individuals, pregnant women, and children. However, experts, including Dr. Duduzile Ndwandwe, a molecular biologist at Cochrane South Africa, caution against jumping to conclusions about its transmissibility and severity, as there are still many knowledge gaps.

Current Situation in South Africa

South Africa has reported 24 cases of mpox in 2024, resulting in three deaths and two active cases. All cases so far have been caused by clade IIb, and no cases of clade Ib have been detected in the country.

De Oliveira advises that while South Africa should not be overly concerned, it must remain vigilant, particularly given the potential for cross-border spread from neighboring countries. Nevashan Govender, Operations Manager of the Emergency Operations Centre at the National Institute for Communicable Diseases (NICD), noted that some milder cases may go unreported, further complicating the picture.

Vaccine and Treatment Efforts

Efforts to contain the outbreak are hampered by limited access to vaccines and treatments. Although the smallpox vaccine is believed to offer some protection against mpox, it has not been widely used in South Africa since the 1980s. Three vaccines—LC16m8, JYNNEOS, and ACAM2000—have been approved for use in some countries, but access remains limited. South Africa has requested a donation of 40,000 doses of the JYNNEOS vaccine to protect those at high risk.

Treatment options are also limited. The antiviral drug tecovirimat, initially developed for smallpox, is being evaluated for use against mpox but is still considered investigational. In South Africa, five patients have received tecovirimat under a special compassionate use protocol.

Public Health Response and Recommendations

Health authorities emphasize that the best defense against mpox is early detection and prevention. Public awareness campaigns are ongoing to educate the public on the signs and symptoms of mpox, which include flu-like symptoms, a distinctive rash, fever, sore throat, muscle aches, headaches, and swollen lymph nodes.

Professor Helen Rees, co-chair of the Incident Management Team on mpox, highlighted the importance of vigilance given South Africa’s high prevalence of immunocompromised individuals, particularly those living with HIV. “We have many people living with HIV in the country, many of whom are on antiretroviral therapy, but we have many others who don’t know their status and might be vulnerable to severe mpox,” she said.

With ongoing efforts to secure vaccines and improve diagnostic capabilities, South Africa remains alert and prepared to respond to any increase in mpox cases