Situational awareness (SA) is one of the two main functions of a biosurveillance system. As Homeland Security Presidential Directive 21 (HSPD-21) states, biosurveillance is “the process of active data-gathering with appropriate analysis and interpretation of biosphere data that might relate to disease activity and threats to human or animal health – whether infectious, toxic, metabolic, or otherwise, and regardless of intentional or natural origin – in order to achieve early warning of health threats, early detection of health events, and overall situational awareness of disease activity” [emphasis added] (US Government, 2007).

Intuitively, most interpret the term “situational awareness” to mean that one is cognizant of one's surroundings. But awareness in this sense is actually only one part of situational awareness. A solid understanding of, and rigorous definition of, situational awareness in a biosurveillance context is critical for being able to assess whether a biosurveillance system, in fact, provides situational awareness, howsuch systems should be modified to improve biosurveillance situational awareness, and whether one system or method provides better situational awareness and thus should be preferred.