Inconsistency of Timeliness in a Chief Complaint-Based Syndromic Surveillance System During Two Influenza Epidemic Seasons

Introduction Syndromic surveillance system has been developed and implemented all over the world, and many studies showed that syndromic data sources had improved timeliness towards traditional surveillance method in the early warning of some infectious disease epidemics. However, owing to the uncertainties of disease epidemic features, clinical manifestations and population behaviors, the early warning timeliness of syndromic data sources might change across time and population, and few studies had explored their consistency in different epidemic periods of infectious diseases.