Comparison of bacterial gastroenteritis cases reported to the sentinel surveillance system and national health insurance claims data in Korea

Bacterial gastrointestinal infections in Korea are monitored through a sentinel surveillance system whose reporting patterns may differ from claims-based healthcare utilization because of differences in reporting coverage, healthcare settings, and diagnostic practices. This study compared temporal, regional, and age-specific patterns between sentinel surveillance reports and National Health Insurance claims and examined potential strengths and structural limitations of the current surveillance system. This study analyzed bacterial gastrointestinal infection patterns in Korea from 2015 to 2023 using 305,802 visit-level NHI claims from 215,360 unique patients and Korea Disease Control and Prevention Agency (KDCA) sentinel surveillance reports. Descriptive statistics, compound annual growth rates (CAGRs), reports per participating sentinel facility, and population-adjusted regional indicators with min–max normalization were used to compare temporal, regional, and age-specific patterns between the two data sources. The number of sentinel surveillance reports increased from 2,374 in 2015 to 10,111 in 2023, while the number of reporting facilities increased from 89 to 211 and reports per facility increased from 26.7 to 47.9. Campylobacter showed a pronounced long-term upward trend in both sentinel reports and claims, with CAGRs of 21.6% and 17.4%, respectively. Regional patterns differed between the two data sources, and adults aged ≥ 65 years accounted for a higher proportion of sentinel reports than claims in 2023 (30.1% vs. 22.0%). Sentinel surveillance and claims data captured different aspects of bacterial gastrointestinal infections. Although absolute counts differed, the sentinel surveillance system reflected major long-term changes in Campylobacter and showed relatively high representation of older adults, while temporal and regional patterns were influenced by changes in reporting coverage and facility distribution. Claims data may therefore serve as a complementary source for interpreting sentinel surveillance patterns rather than as a reference standard for true incidence.