Signal detection of substance-related emergency department visits during UEFA EURO 2024 in Germany: enhancing public health surveillance for future mass gatherings.

Introduction: Germany hosted the men's UEFA European Championship (EURO 2024) in summer 2024, attracting millions of visitors across multiple cities. Mass gathering events (MGEs) can rapidly alter social environments which impact substance use behaviors, potentially increasing demand on local healthcare systems. In response, the German national public health institute (Robert Koch Institute, RKI) piloted substance-related indicators using routine emergency department (ED) data from the Emergency Department Data Registry throughout the tournament to explore their applicability for real-time emergency department surveillance. Methods: We aimed to monitor substance use patterns in ED visits during EURO 2024 by developing an umbrella syndrome definition for psychotropic substance intoxication (SATX) and two more specific syndrome definitions for acute alcohol intoxication (ATX) and substance intoxication other than alcohol (STX), based on diagnoses, chief complaints, and age criteria. Descriptive analyses compared identified cases during the tournament period (14 June-14 July 2024) with a reference period. Analyses were stratified by sex, age group, and triage level. A quasi-Poisson regression model was used to estimate expected values and 95% prediction intervals (95% PI) for each indicator during the tournament period. Signals were detected when observed case counts exceeded the upper threshold of the 95% PI. Results: Between 1 January 2018 and 9 September 2024, 5,602,933 visits from 39 EDs were included. Across both the tournament and reference periods, SATX, ATX, and STX cases were more common among males, particularly for ATX. Most SATX and ATX cases occurred among individuals aged 30-59 years, whereas STX cases were most frequent among those aged 20-39 years. Relative increases in triage level 4 cases were observed during the tournament period. During EURO 2024, signals exceeding the upper threshold of the 95% PI were detected for all indicators, including 16 SATX, three ATX, and 13 STX signals. The largest deviation was observed for SATX on 29 June 2024, with 127 observed cases compared to 74 expected cases. Conclusion: This study demonstrated that rapid changes in substance-related ED utilization during MGEs can be effectively monitored using the syndrome definitions and signal detection methods, whose application can support public health surveillance during future events.