Ecology

MPXV is thought to be maintained in nature through a complex, multi-host reservoir system rather than in a single definitive animal species. Small mammals, particularly African rodents such as rope squirrels (Funisciurus spp.), Gambian pouched rats (Cricetomys spp.), dormice (Graphiurus spp.) and striped mice (Hybomys spp.), are considered the most plausible reservoir or amplifying hosts, while non-human primates are regarded as incidental spillover hosts.

 

Spatial overlap analyses of ecological niches for African mammal species and human cases consistently identified squirrels (particularly rope squirrels) as the most likely source of human infections[1]. However, there is little direct evidence of transmission from these animals to humans.

​

A recent outbreak of MPXV in wild sooty mangabeys (Cercocebus atys) in Côte d’Ivoire was shown to be linked to transmission from the fire-footed rope squirrel (Funisciurus pyrropus), on which monkeys feed[2]. This suggests wildlife hunting and consumption as a potential transmission route to primates, including humans (consistent with epidemiological studies in the 1980s in the DRC on risk factors for transmission). Field studies and experimental infections suggest that some rodent species can sustain prolonged infection and shed high viral loads via saliva, faeces, urine and respiratory secretions, facilitating environmental contamination and zoonotic transmission.

​

Distinct clade-specific host associations have been observed. Clade I viruses are overwhelmingly sampled from humans, consistent with endemic circulation and repeated spillover in Central Africa, whereas clade IIa viruses are more frequently isolated from animals, suggesting differences in surveillance intensity, host susceptibility, or transmission efficiency.

 

A US outbreak in 2003 of 72 cases, for example, was linked to MPXV transmission from imported African animals to prairie dogs followed by prairie dog to human infection[3].

​

​