For decades, the origins of the mpox virus (formerly known as monkeypox) remained a frustrating riddle for scientists. Despite its name, monkeys were never the primary source of the disease; they were merely “accidental hosts,” much like humans. However, a groundbreaking study published in February 2026 has finally provided a “smoking gun” that points to a likely natural reservoir: the African rope squirrel.
The Breakthrough in Taï National Park
The discovery unfolded in the dense rainforests of Côte d’Ivoire’s Taï National Park. Researchers from the Helmholtz Institute for One Health (HIOH) had been monitoring a group of sooty mangabeys (Cercocebus atys) when an outbreak erupted in early 2023. Roughly one-third of the monkey troop fell ill with telltale skin lesions, and tragically, four infants died from the infection.
Because the researchers had been conducting long-term surveillance, they were able to act like forensic detectives. By analyzing fecal samples and genetic data, the team, led by veterinarian and disease ecologist Livia Patrono, traced the outbreak back to a specific event: a mangabey eating a fire-footed rope squirrel (Funisciurus pyrropus).
Finding the “Smoking Gun”
As detailed in the Science News report, the evidence was remarkably precise. Approximately twelve weeks before the monkey outbreak began, researchers found a fire-footed rope squirrel carcass just three kilometers away that tested positive for mpox.
Further investigation of the mangabeys’ diet provided the missing link. While mangabeys primarily eat fruit and nuts, they occasionally hunt small rodents. Archival video from 2014 had already captured a mangabey consuming a rope squirrel, confirming the behavioral pathway for transmission. Most importantly, the team found a fecal sample from the first infected monkey that contained both mpox DNA and the DNA of a fire-footed rope squirrel. This confirmed that the monkey had consumed the squirrel shortly before falling ill.
Why Squirrels are the Perfect Reservoir
The search for the mpox reservoir has focused on rodents for years. According to the World Health Organization (WHO), while many animals are susceptible, a true “reservoir” must be able to carry and circulate the virus permanently in the wild.
Rope squirrels have long been the top suspects for several reasons:
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Historical Evidence: The first mpox virus ever isolated from a wild animal came from a Thomas’s rope squirrel in 1985.
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Long-term Presence: Museum specimens of squirrels dating back to 1899 have tested positive for the virus, suggesting it has lived in these populations for over a century.
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Geographic Overlap: The habitats of various rope squirrel species align almost perfectly with the regions in West and Central Africa where human mpox outbreaks frequently begin.
Implications for Human Health
Identifying the fire-footed rope squirrel as a primary source is a major victory for public health. Mpox is a zoonotic disease, meaning it jumps from animals to humans. In many parts of Africa, as larger game becomes scarce, local communities have turned to hunting smaller rodents like squirrels for food.
As noted by the Institut Pasteur, human activities like deforestation and urbanization are pushing people deeper into wildlife habitats, increasing the frequency of these “spillover” events. Knowing exactly which species carries the virus allows health officials to create targeted prevention strategies—such as teaching proper hygiene for handling small game or providing personal protective equipment to those working in high-risk forest areas.
The Road Ahead
While the fire-footed rope squirrel is a primary culprit, scientists caution that it may not be the only one. The virus is likely maintained by a complex web of different rodent species across the African continent. However, this study marks the first time researchers have witnessed the “jump” from a reservoir to another species in the wild, providing a roadmap for how to track and eventually stop the next human epidemic before it starts.
Sources & Further Reading:
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Science News: An African monkey ate a rope squirrel and came down with mpox
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Helmholtz Institute: Fire-footed rope squirrels identified as a natural reservoir
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World Health Organization: Mpox Fact Sheet
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Institut Pasteur: Mpox History and Research
