Modelling international spread of clade IIb mpox on the Asian continent.

Objective: To understand and simulate international spread of the disease mpox, considering variations in sexual activity levels and international travel among men who have sex with men. Methods: We developed a mathematical model that considers differing sexual networks and the volume of international travel among men who have sex with men, calibrated to disease incidence data in Japan. We then used our model to simulate the potential international spread of mpox across 42 countries and territories on the Asian continent, assuming Japan as the origin of spread. Findings: Our simulations identified countries and territories at a high risk of mpox introduction, many being low- and middle-income countries and territories in the Western Pacific and South-East Asia regions. We found that the simulated risk of importation gradually shifted over time from the Western Pacific to the South-East Asia region, and later to the Eastern Mediterranean and European regions. This simulated pattern broadly aligns with actual mpox spread patterns observed between 2023 and 2024. Conclusion: Our multicountry model for mpox outbreaks can help project the possible trajectory of mpox spread across countries and territories on the Asian continent. Our findings warrant global efforts to contain mpox outbreaks, particularly support for low- and middle-income countries and territories which are at higher risk of introduction, so that the risk of continued spread across the Asian continent and beyond is reduced.