Risk of evolution driven population-wide emergence of mpox: The paradoxic effect of moderate interventions

The global mpox outbreak in 2022 was declared a public health emergency of international concern. While in non-endemic countries disease spread remained limited mostly to a high risk group, a main public health concern is that through evolution, mpox gains the ability to widely spread in the entire population.

We construct a stochastic epidemiological model of SEIR type, to investigate the spread of mpox primarily propagating within a core population - consisting of MSM individuals having multiple sexual partners - before affecting the general population. We examine how effective various intervention strategies are in preventing this from happening. These non-pharmaceutical interventions include reducing disease transmission in the core population, in the general population, or in both. Our analysis encompasses the optimal timing for these interventions, considering the effects of early versus late intervention and the potential impact of different mutation patterns on disease spread.

Our findings highlight that effective early intervention can be achieved with lower intensity, while delayed intervention requires stronger measures. Notably, our results reveal an intriguing phenomenon where moderate intervention could lead to worse outcome than no intervention. This counterintuitive outcome arises because moderate reductions may prolong transmission chains within the core group, leading to more opportunities for the pathogen to acquire mutations resulting in higher transmission potential in the general population.

A comprehensive understanding of the role of the core group in disease dynamics and the mutation patterns are crucial for developing tailored and effective public health strategies. The moderate intervention paradox suggests that to minimize the risk of population-wide emergence, it must be ensured that targeted interventions are highly efficient.