Temporal and age-structured analysis of Mpox spread in the 2022 Global outbreak: data-assimilation insights for epidemic control.

Abstract

Background: The global outbreak of mpox that began in 2022 caused sustained human-to-human transmission and demonstrates distinct epidemiological characteristics compared to previous outbreaks. Our aim is to quantify temporal variation of mpox transmissibility within or between age groups and evaluate the effectiveness of interventions in real time.

Methods: The data used in this study is sourced from publicly available mpox confirmed cases data provided by WHO. We divided population into four age groups and constructed a transmission dynamics model with age structure of the population. And we estimated the transmissibilities of the monkeypox virus within or between age groups in real time by assimilation of global surveillance data from WHO, and performed intervention simulations in different scenarios we set up.

Results: The effective reproduction number of mpox in the 18-44 age group is significantly higher than in other age groups, and it initially experiences a rapid increase, enters a phase of steady decrease after reaching a certain point [ $R_{22}=1.33$ , 95% credible interval (CrI): 1.10-1.56]. Earlier implementation of interventions yields both superior effectiveness and greater cost-efficiency. Emergency vaccination for whole population initiated on June 15, 2022 reduced cumulative infections by 67.43% (95% CrI: 62.15-72.71) at only 40% coverage, whereas vaccination starting August 1, 2022 achieved only 47.86% (95% CrI: 42.70-53.01) reduction at 90% coverage. And high-risk-targeted and population-wide interventions showed limited effectiveness differences. Case management (3-day mean infectious period) initiated on July 15 achieved cumulative infection reductions of 59.84% (95% CrI: 54.28-65.40) when targeting the whole population, compared to 56.80% (95% CrI: 49.24-64.35) reduction when targeting only high-risk groups (aged 18-44 years).

Conclusions: The transmissibility of mpox within the 18-44 age group follows a distinct pattern of rapid growth-slow decline not observed to the same extent in other age groups. Real-time estimation of mpox transmissibility within or between age groups helps us to understand the dynamic process of mpox interpersonal transmission better and evaluate the effect of various interventions in real world more promptly.