Speaker
Description
Previous studies have identified several drivers of influenza-like illness (ILI) incidence dynamics in temperate regions, yet it remains unclear whether these associations are reproducible across countries or shaped by local context. This study quantifies the relative contributions of climate and behavioral factors to ILI incidence dynamics across multiple European countries, using weekly incidence data from 2014 to 2025 reported to ERVISS, the surveillance database maintained by ECDC. We compute the weekly effective reproduction number ($R_e$) from incidence data and model them as a function of explanatory variables within a regression framework. These variables include absolute humidity, holiday periods, and the Normalcy Index. The framework separates persistent associations from season-specific baseline components and reporting-related variation, and enables comparison between pre- and post-pandemic periods. We find that absolute humidity shows consistent negative associations with weekly $R_e$ across countries, whereas behavioral factors exhibit greater heterogeneity. This framework provides a way to distinguish between generalizable and context-dependent drivers by comparing cross-regional dynamics, informing interpretation of epidemic trends during both normal and disrupted periods, such as the COVID-19 pandemic.
