A time-varying risk assessment framework for P. vivax malaria transmission in temperate settings: A case study of the Republic of Korea

Understanding the time-varying transmission potential of Plasmodium vivax is essential for guiding elimination efforts, particularly in low-transmission, temperate regions where the seasonal vector activity and the complex biology of the parasite present unique challenges. Here we develop an integrated modelling approach to estimate the time-varying case reproduction number of P. vivax malaria in the Republic of Korea, using weekly data on temperature, malaria activity index, and symptom onset from the primary endemic regions between 2013 and 2025. The model integrates temperature-dependent and seasonally constrained serial intervals to reconstruct the transmission timeline and infer likely transmission links between cases without requiring phylogenetic or contact-tracing data. Our findings reveal that although the greatest number of secondary cases is generated during the summer transmission months (June to August), the average case reproduction number is highest during the pre-transmission season (October to April), indicating that cases arising in the pre-transmission season has a higher potential to generate further infections compared to cases in other seasons. This underscores the need for enhanced case detection, diagnosis, and treatment during the pre-transmission period. To make these patterns explorable, we provide a web-based interactive tool that links each case to the infections it seeds, revealing transmission that crosses years. This modelling framework relies only on routinely collected surveillance and environmental data, offering a transferable tool for resource-constrained or pre-elimination settings where genetic or contact-tracing data are unavailable.