Mpox, Why Does It Matter?

On August 14th, 2024, the World Health Organization (WHO) once again declared Mpox a Public Health Emergency of International Concern (PHEIC), marking the second declaration in a span of three years. Since 2007, only seven other infectious diseases have been classified as PHEIC by the International Health Regulations (IHR).

A disease or event is classified as a PHEIC if there is potential to spread across countries and international borders. The most recent declaration of Mpox as a PHEIC follows the emergence of a deadlier and more infectious variant observed within the Democratic Republic of Congo and its rapid spread to neighboring and extracontinental countries.

Mpox, formerly known as monkeypox, is a viral zoonotic disease known to cause painful fluid-filled lesions, fever, muscle aches, low energy, and sore throat. In some cases, people may die from complications. Mpox has been circulating in Central and West Africa since the 1970’s. For decades, researchers have studied the interconnection and consequences of interactions between the health of humans, animals, and the environment. Coined as the One Health Approach, public health experts explore how overlapping factors including close human-animal interaction, environmental changes such as deforestation and climate variability, and human mobility can facilitate the spread of zoonotic diseases such as Mpox.

Clade I which predominantly circulates in Central Africa, was originally transmitted through animal-to-human contact, making zoonotic transmission the primary concern. In contrast, Clade II, more common in West Africa, has evolved to spread more easily through human-to-human transmission, posing a different set of public health challenges.

Clade Ib—part of the Clade I family—is the more deadly variant of the disease. At first, the infection occurred in humans only through bites or scratches from affected animals, also known as zoonosis. On the contrary, Clade IIb—part of the Clade II family—is milder and has human-to-human transmission capacities. What worries public health officials is not only that Clade Ib is the main circulating clade responsible for the current outbreak in the Democratic Republic of Congo, but also that Clade Ib is now able to spread among humans. This shift in transmission dynamics allows the virus more opportunities for mutation, potentially increasing the severity of the disease.

Between January 2022 and June 2024, an estimated 100,000 people in 116 countries were infected, resulting in approximately 200 deaths, the majority of which were among children. Most deaths have been linked to Clade Ib, which has been circulating predominantly in Africa. In contrast, a milder variant of Mpox circulating in regions such as the United States and Europe, combined with access to vaccines, medical care, and enhanced surveillance, has resulted in lower severity and mortality in these regions. The alarming rise in Mpox cases within the Democratic Republic of Congo, along with the spread to an increasing number of countries both within and outside of Africa, has raised serious concerns. A recent article in The Lancet highlights how changes in transmission dynamics, the international spread of the infection, and increased human mobility are contributing to the growing risk of a new global pandemic.

This sudden appearance of Mpox in countries where the virus has previously not been reported underscores the need for a global strategy that explicitly takes into account the interconnectedness between humans, animals, and ecosystems, now referred to as the One Health Approach. The WHO’s declaration of Mpox as a PHEIC for the second time in less than three years—two of which occurred in the context of a global pandemic—reinforces this urgency.

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