Modelling the effectiveness of isolation strategies for managing mpox outbreaks with variable infectiousness profiles

The global outbreak of mpox (formerly monkeypox) in 2022 raised public awareness about the disease. The ensuing sporadic outbreaks in 2023 highlighted the importance of sustaining nonpharmaceutical interventions, such as case isolation and contact tracing. Using viral load data, we developed a modelling framework to characterize the various infectiousness profiles of infected individuals. We used this model to examine the potential effectiveness of two different possible isolation rules: specifically, rules permitting infected individuals to stop isolating after either a fixed-duration or following negative tests for infection. Our analysis showed large individual variations in the duration of viral shedding, ranging from about 23 to 50 days. The risk of infected individuals ending isolation too early (i.e., while they remained an infection risk) was estimated to be about 5% after 3 weeks of isolation. Unnecessary isolation after the end of the infectious period could be reduced by use of a testing-based rule. These findings support the choice of a 3-week isolation period following symptom onset if a fixed-duration rule is used, but also demonstrate how testing can mitigate unnecessarily prolonged isolation for those who have shorter infectious periods.