Dynamic shift in the dominant transmission route of clade Ib mpox virus across networks with sexual and non-sexual contacts

The intensifying outbreaks of the novel monkeypox virus clade Ib in the Democratic Republic of the Congo have raised global concern about the potential for wider epidemic spread. Some clade Ib mpox outbreaks have shown a distinct transmission pattern in which transmission associated with both sexual and non-sexual contacts co-exist. Here, we characterize these outbreaks in a network epidemic model, which incorporates sexual and non-sexual contacts, and project age- and route-specific transmission potentials under a wide range of scenarios. Our analyses suggest that the dominant route of transmission may shift over time from sexual to non-sexual contacts, which leads to larger epidemics. The age groups contributing most to overall infections and mortality also change over time, suggesting that target groups for intervention should be adjusted accordingly. For countries at risk of travel-associated mpox outbreaks, these findings highlight the importance of monitoring evolving monkeypox virus transmission patterns and interacting transmission routes to support timely and effective control measures. Significance statementThe initial outbreak of clade Ib monkeypox virus in the Democratic Republic of Congo was characterized by differences in how the virus spreads, with transmission through both sexual and non-sexual contacts playing a crucial role. This study addresses two key public health challenges: how does an outbreak evolve when multiple transmission routes coexist, and how to translate that understanding into effective interventions. We develop a mathematical framework to address these challenges and show that the dominant transmission route can shift over time, from sexual to non-sexual. We show that even small increases in transmission through non-sexual contacts can lead to substantially larger epidemics, underscoring the need for continuous monitoring and adaptive response strategies. One sentence summaryDuring an mpox outbreak, the dominant route of transmission and optimal target groups for intervention may shift over time