Table 3.

Description of different surveillance system

	Description
Syndromic surveillance38, 39, 40, 41, 42, 45, 46, 47, 58, 68, 69, 70	The following clinical data was used: chief complaint and presentation, discharge diagnosis, free text analysis of the entire medical record, calls to triage and help lines, ambulance dispatch calls, discharge diagnosis, ambulance dispatch data that successfully identified the expected annual epidemics of influenza
Laboratory surveillance73	Slow and insensitive in rapid detection a large-scale infectious disease outbreak
Medication sales74, 75, 76, 77, 78, 79	Over-the-counter drug sales correlated with influenza activity
Self-reporting participatory systems81, 82, 83	Online-based surveillance system relying on voluntary participation
Informal surveillance and epidemic intelligence85, 86, 87, 88, 89, 90, 91, 92, 93, 94	Detect relevant information from the internet, nationally and internationally