Establishing and validating syndromic surveillance of gastrointestinal infections using routine emergency department data, Germany, 2019–2023

Gastrointestinal infections in Germany account for 24.5 million outpatient visits annually. To enhance outbreak detection and trend monitoring, we developed and validated a syndrome definition for syndromic surveillance of gastrointestinal infections in emergency departments. We selected presenting complaints (Canadian Emergency Department Information System) and diagnoses (ICD-10) to develop the syndrome definition. Validation involved cross-correlation analysis of syndromic and laboratory-based surveillance trends (norovirus-gastroenteritis, rotavirus-gastroenteritis, campylobacteriosis and salmonellosis notifications). We included emergency departments from the German AKTIN registry with continuous data transmission (01/2019-06/2023). Our novel syndrome definition combined complaints (diarrhoea, vomiting, nausea) and diagnoses (intestinal infectious diseases). Across 864,353 visits in 7 emergency departments, 2.1% (n = 18,158) were gastrointestinal infection cases. Of those, 57% (n = 10,424) were female; 23% were aged 0-19 years (n = 4108); and 23% 20-39 years (n = 4116). Trends were similar between surveillance systems. Cross-correlation was 0.73 (95%-confidence interval 0.61-0.85; p < 0.001) at lag - 1, indicating a 1-week relative reporting delay of laboratory-based surveillance. Coherent trends and significant cross-correlation validated our syndrome definition. This novel automated syndromic surveillance complements laboratory-based surveillance while offering improved timeliness and reduced workload. Therefore, it was implemented in Germany's national routine surveillance of emergency departments.