Retrospective modelling of space-time clusters of acute gastrointestinal syndromes in Lombardy, Italy

Abstract Gastrointestinal (GI) syndrome encompasses complex symptoms characterised by preventability, high morbidity, and relatively low mortality. We conducted this study to investigate the ability of syndromic surveillance for detecting space–time clusters of acute GI syndromes in Lombardy, Italy. The target population included the 10 million beneficiaries of the Regional Health Service during 2023. Individuals who experienced at least one Emergency Department (ED) admission for GI syndrome in 2023 were considered the main syndromic cases of interest, with retrospective data obtained from healthcare utilization databases. Two secondary case definitions, based on reports of GI infective disorders and drug dispensations for treating GI disorders, were also used. Daily data at the level of all 86 health districts composing Lombardy Region were monitored. By comparing observed and expected cases, space–time scan statistics were used to detect clusters within specific time frames and areas. Analyses were performed using SaTScan software. In 2023, 33.3 cases per 100,000 person-weeks were admitted to the ED for GI disorders. Based on the secondary definitions of cases, detection rates of 0.42 and 19.2 cases every 100,000 person-week were observed, respectively. Overall, 11 clusters were detected across 17 health districts, with durations ranging from 1 to 3 days. Clear positive linear trends were observed across the 86 health districts between ED-based rates and the corresponding reporting-based and drug-based rates. A syndromic surveillance system for acute GI syndromes is a promising tool for supporting policymakers in anticipating the emergence of new epidemics and evaluating the impact of actions aimed at reducing the risk of acute GI disturbances in endemic areas.