Is there a risk of mpox spreading from humans back to animals?
Mpox is a zoonotic disease caused by the monkeypox virus (MPXV). The virus is transmitted from animals to humans in endemic areas in central and western Africa. Although the natural ecology of MPXV remains to be elucidated, evidence points towards several rodent species acting as reservoirs and possibly vectors. Mpox has also been reported in other species, including non-human primates, suggesting a wide host range. Since 2017, sustained human-to-human transmission via close contact has resulted in the largest mpox outbreaks ever recorded.
Cases of mpox have been reported in more than 110 countries since 2022, mostly in places where the disease had not previously been recorded and where zoonotic transmission does not occur. This global emergence included cases recorded in South Africa in 2022, 2024, and early 2025.
Given the proposed wide host range of MPXV and the increased occurrence of human cases, concerns have arisen about reverse zoonoses, where the virus transmits from infected persons to animals, including rodents, non-human primates, and domestic animals, potentially fuelling new chains of transmission.
Background
Mpox is an infectious disease caused by an orthopoxvirus, orthopoxvirus monkeypox virus (MPXV). It was first identified in 1958 in cynomolgus monkeys (Macaca fascicularis) kept for research purposes. The natural ecology of MPXV remains elusive, with no active animal surveillance and limited research. A meta-analysis of MPXV infection in animals reported findings from fewer than 3,000 subjects.
Before 2022, mpox was considered a rare zoonotic disease in humans, with only occasional transmission in West and Central Africa. Zoonotic transmission is presumably through direct contact with skin wounds, scabs, rashes, or infected bodily fluids and secretions. Exposure through bites and ingestion of bush meat has also been associated with cases. However, the true reservoirs remain unknown, and the routes of animal-to-human transmission are uncertain. Human-to-human transmission is typically restricted to close contact, often within households.
Discussion
The unprecedented global outbreak of mpox raises concern about the risk of MPXV transmission from humans to animal hosts, particularly companion animals. Several international agencies recognise the potential for reverse zoonoses from infected humans to companion animals.
This concern relates to the virus’s wide host range and increased circulation. Evidence of various species being susceptible raises the possibility of new chains of virus transmission. However, there is little information about which species are merely susceptible and which can sustain productive infection capable of onward transmission. The natural reservoir or reservoirs of MPXV remain undetermined. Surveillance for mpox in companion animals has been very limited. Reports from the United States and United Kingdom have not identified any such cases during the multi-country outbreak, even when human case numbers were high.
Conclusion
Available evidence indicates a low risk of MPXV transmission from infected persons to rodents, non-human primates, and domestic animals. However, due to limited data, the risk cannot be dismissed entirely, and a cautious approach remains valid.
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