Based on the definition of the U.S. Centers for Disease Control and Prevention (2), an updated definition of syndromic surveillance was developed, taking into account the evolution of syndromic surveillance in the past decade. Further, an inventory of syndromic surveillance systems in Europe has been started. To identify human syndromic surveillance systems, a literature review was first performed using Pubmed and Google, identifying 40 relevant publications. A brief questionnaire was sent to Triple-S partners, the European Center for Disease Prevention and Control (ECDC) and other contact persons to identify existing, past, pilot and planned systems in the different countries and the reference person for each system. The reference persons were then asked to complete a long online questionnaire for collecting detailed information (e.g., objectives, data sources, timeliness, statistical methods for outbreak detection, reporting tools and response measures).