Nurses at the triage stations at all participating hospitals generated the bulk of the information needed for syndromic surveillance. That information included time and date of admission, date of birth, gender, home zip-code, body temperature, triage categories and chief complaints for patients admitted to their EDs. Because the National Health Insurance requires hospitals to keep clinical data written in ICD-9 codes based on the criteria of the international classification of diseases, 9th revision, clinical modification (ICD-9-CM) for billing purposes, we were also able to collect clinical data from initial assessment of each case by an ED physician. These fundamental data were provided in either the health level-seven protocol (HL-7) format or extensible Markup Language (XML) format, if HL-7 was not used by a hospital during the time of the study. Thus, ED-SSS is capable of accepting these data of above-mentioned variables (Table 1) , including the patients' clinical and demographical information, and hospital identification numbers, in either format.