A bio-surveillance system monitors symptoms or groups of symptoms experienced by people in a geographical area. The system tracks symptoms reported by calls to an emergency service dispatcher. The bio-surveillance system monitors the symptoms and associates the geographical location with the symptoms. Various triggers are programmed and stored in the system to look for certain types of threats. Each trigger is set based on a statistical variation of the historical data relating to the symptoms within a predetermined time in a predefined geographical area. When the reported symptoms exceed one of the triggers, an alert is activated to provide an indication of a potential biological or chemical terrorist attack.