African Monkey's Squirrel Meal Linked to Mpox Outbreak, First Wild Species-to-Species Transmission Documented

Côte d’Ivoire - Ekhbary News Agency

African Monkey's Squirrel Meal Linked to Mpox Outbreak, First Wild Species-to-Species Transmission Documented

Scientists have documented a groundbreaking instance of the mpox virus jumping between different wild animal species for the first time, shedding new light on the complex transmission cycles of the pathogen. The event occurred in early 2023 when an outbreak of mpox erupted among a group of sooty mangabeys (Cercocebus atys) in Taï National Park, Côte d’Ivoire. The disease affected approximately one-third of the monkey troop, including infants, and tragically resulted in the deaths of four young individuals.

Subsequent wildlife surveys and genetic analysis by researchers suggest that the outbreak may have been sparked by a dramatic event: one of the mangabeys consuming an infected fire-footed rope squirrel (Funisciurus pyrropus). The findings, published on February 11, 2026, in the prestigious journal Nature, offer critical insights into how mpox circulates within wildlife populations, a crucial step in understanding and preventing future human outbreaks.

Viral spillover events from animals to humans are the primary origin of human mpox epidemics. However, identifying the specific animal hosts and understanding the pathways of transmission within wildlife reservoirs remain significant challenges for epidemiologists and wildlife health experts. This new study provides compelling evidence for animal-to-animal transmission in a natural setting, moving beyond the typical focus on zoonotic transmission to humans.

Dr. Livia Patrono, a veterinarian and disease ecologist at the Helmholtz Institute for One Health in Greifswald, Germany, who led the research, explained the long-standing question that motivated the study: "One big question for us has been, ‘where are the nonhuman primates getting infected from?’" For years, researchers have suspected that rodents, particularly squirrels, might serve as a significant reservoir for the mpox virus. The first isolation of the monkeypox virus from wildlife was indeed from a Thomas's rope squirrel (F. anerythrus), and the habitats of various rope squirrel species frequently overlap with areas where human mpox epidemics have previously emerged. The virus's historical presence in these animals is further underscored by findings of mpox virus in museum specimens of rope squirrels dating back to 1899.

Through extensive wildlife monitoring, including the collection and testing of fecal samples from across the park and necropsies of deceased animals, Dr. Patrono and her colleagues meticulously investigated the origins of the 2023 outbreak. The team screened over 700 rodents that were trapped or found dead. Remarkably, only one rodent tested positive for the mpox virus: a fire-footed rope squirrel found deceased approximately 3 kilometers south of the sooty mangabey territory. This squirrel was discovered just 12 weeks prior to the onset of the mpox outbreak in the monkeys.

While this specific deceased squirrel might not have directly initiated the large-scale outbreak, genetic analyses provided a crucial link. The mpox virus found in the squirrel was closely related, though not identical, to the strain that sickened the sooty mangabeys. This genetic proximity strongly suggests that another infected fire-footed rope squirrel, likely consumed by a mangabey, served as the source of the infection.

The research team also leveraged behavioral observations and collected evidence. Video footage from 2014 had previously documented a sooty mangabey in the same park consuming a fire-footed rope squirrel. To confirm if such predation had occurred recently, the researchers analyzed fecal samples from the mangabey troop collected before the 2023 outbreak. Two samples tested positive for DNA from the fire-footed squirrel, indicating recent consumption. Critically, one of these samples also contained mpox virus DNA and was linked to the mangabey believed to be the index case of the outbreak.

"That was a pretty, let's say, informative piece of evidence saying that [a fire-footed rope squirrel] was a very likely source of infection for the mangabeys," Dr. Patrono stated. This finding elevates the understanding of mpox beyond human-to-human transmission and zoonotic spillover from animals to humans, emphasizing the potential for complex ecological transmission chains.

Dr. Clement Meseko, a veterinarian and virologist at the National Veterinary Research Institute in Vom, Nigeria, who was not involved in the study, commented on the significance of these findings. "Pinpointing which animals carry the virus can help guide prevention measures that protect people from getting infected," he noted. Public health officials might consider advising communities living near known squirrel habitats to take precautions, such as wearing personal protective equipment when handling squirrels or practicing rigorous hand hygiene.

Taï National Park has been a site of multiple mpox outbreaks among primates since 2012. Prior incidents include a deceased infected sooty mangabey in 2012 and outbreaks among chimpanzee groups (Pan troglodytes) in 2017 and 2018. However, these events did not indicate that primates were the natural reservoir; rather, mpox appeared to circulate in these populations only during epidemic phases. The consistent question remained: what was the source of the initial infection for these primates?

This study offers a compelling answer, identifying rope squirrels as a likely bridge for the virus into primate populations. It also suggests that other rodent species could potentially harbor the virus, posing additional risks. Continued, intensive wildlife monitoring and research into the ecological dynamics of mpox are essential for anticipating and mitigating future health threats posed by this adaptable virus.

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