Reasons patients present to the emergency department might change during epidemics and be a valuable component of a disease surveillance system.

We hypothesize that the frequency of reasons patients present to the emergency department will change during epidemics and might be a valuable component of a disease surveillance system. We found support for this hypothesis over a two-year period with high frequency days of fever clustering during two periods of increased hospital influenza activity, but not during any other period during the two-years. This methodology appears to be superior to the previous use of triage nurses defining patients with symptom complexes. Such a system could result in online monitoring, be independent of the medical personnel (use of admission secretary), and might be able to identify various epidemics including increased hospital disease activity due to bio-terror attacks, influenza, and food poisoning. This would have important implications for limiting the spread of disease and for the acute planning of distribution of medical resources. Studies are warranted in various settings to determine whether or not changes in the daily frequencies of reasons patients present to the ED will allow identification of epidemics.