Syndromic surveillance for infectious disease outbreaks using chief complaint data.

Although the ubiquitous threat of biochemical terrorism has spurred newfound interest in disease surveillance, the current set of systems lacks the necessary ability to rapidly detect and report an outbreak. By focusing on real-time analysis of patient chief complaint data, this investigation sought to eliminate the inherent delay in current surveillance systems. The objective was to compare a real-time computerized tracking system to rapid laboratory testing for disease surveillance using influenza as a model. All patients presenting to the adult and pediatric emergency departments of a university teaching hospital with chief complaints of "fever" and "flu-like illness" from October 2004 through December 2004 were included. Using a computerized patient tracking system, patient age, sex, chief complaint, and zip code were collected and correlated with the documented outbreak of the 2003-2004 influenza season as indicated by the total daily number of positive rapid influenza tests. Determinations of whether an increase in the number of chief complaints of concern was based on the CUSUM statistic. In addition, this surveillance data was also compared to chief complaint data collected from many emergency departments within the Nashville area by the Metropolitan Nashville Health Department. It was found that, although chief complaints of flu or fever effectively mirrored final diagnosis, our surveillance system did not appreciably improve use of rapid influenza testing. The real-time nature of this investigation, however, yielded a novel use for this system in its predictive ability concerning the course of the outbreak and subsequent allowance for improved hospital response time through informed staffing decisions. Although our findings indicate that surveillance from a single institution may not result in a more effective outbreak detection in a moderate sized city, they also suggest that real-time analysis of this evolving outbreak would prove valuable in mounting an effective medical response.

Robert G. Thomas, MSI, Robin R. Hemphill, MD, and Dominik Aronsky, MD, PhD. Vanderbilt School of Medicine, Nashville, TN.