Temporal Correlation of Nontraditional and Traditional Evidence of a Natural Outbreak

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Douglas Stetson, R. Bloom, D. Crary, K. Cheng, G. McClellan
General Dynamics Advanced Information Systems, Arlington, Virginia

Corresponding author: Douglas Stetson, 1400 Key Blvd., Ste. 100, Arlington, VA 22209. Telephone: 757-377-5283; E-mail: douglas.stetson@gd-ais.com.

Abstract

Introduction: Although syndromic surveillance typically involves monitoring of traditional clinical data sources (e.g., emergency department visits), monitoring nontraditional sources might also provide information about community health. This study demonstrated that parking use data from a medical center parking facility reflected an unusual increase in regional outpatient visits for respiratory illness associated with a well-publicized public health event.

Objective: This study aimed to determine whether a nontraditional source (i.e., parking facility use data) reflected a sudden communitywide surge in health-care facility use associated with widespread news coverage of an unexpected local cluster of respiratory illness-related deaths among children.

Methods: Two data sources were collected and compared for the period in which the cluster occurred: 1) daily parking facility use data from a parking structure serving a medical center complex and 2) regional counts of outpatient respiratory visits to military treatment facilities made by military members and their families. Daily localized forecasts of expected parking use and outpatient visits were generated on the basis of recent historic counts to reduce cyclic influences (e.g., day-of-week effects). Daily variations in parking and clinic volume and differences between actual volume and forecast volume were analyzed for statistical significance.

Results: A statistically significant increase in actual parking facility use compared with expected use was identified, coincident with both the statistically significant increase in actual outpatient respiratory visits compared with forecast visits and with the period of local news reporting on the cluster of deaths (February 23--25, 2003) (Figure). No other variations in the parking or outpatient-visit data during that calendar quarter had similar statistical significance.

Conclusion: Syndromic surveillance efforts can be supported by standard analytic and statistical examination of nonclinical, real-world data.

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