Quantifying the basic reproduction number and the under-estimated fraction of mpox cases around the world at the onset of the outbreak: a mathematical modeling and machine learning- based study

In 2022, there was a global resurgence of mpox, with different clinico-epidemiological features compared with previousoutbreaks. During this resurgence, sexual contact was hypothesized as the primary transmission route, with the communityof men having sex with men (MSM) being disproportionately affected. Because of the stigma associated with sexuallytransmitted infections, especially those impacting MSM, the real burden of mpox could be masked.We quantified the basic reproduction number (R0) and the under-estimated fraction of mpox cases in 16 countries, from theonset of the outbreak until early September 2022, using Bayesian inference and a compartmentalized, risk-structured (high-and low-risk populations), two-route (sexual and non-sexual transmission) mathematical model. Machine learning (ML) wasleveraged to identify under-estimation determinants.Estimated R0 ranged between 1·37 (Canada) and 3·68 (Germany). The under-estimation rates for the high- and low-riskpopulations varied between 25-93% and 65-85%, respectively. The estimated total number of mpox cases, relative to thereported cases, is highest in Colombia (3·60) and lowest in Canada (1·08). In the ML analysis, two clusters of countries couldbe identified, differing in terms of attitudes towards the 2SLGBTQIAP+ community and importance of religion.Given the substantial mpox under-estimation, surveillance should be enhanced and campaigns against the stigmatization ofMSM should be organized. Countries have different social characteristics, potentially explaining the various degrees of under-reporting in mpox cases, which should be considered by studies assessing the effectiveness of community-basedinterventions.