title: Ambulatory-care diagnoses as potential indicators of outbreaks of gastrointestinal illness--Minnesota.
abstract: BACKGROUND
  Syndromic surveillance's capability to augment existing surveillance for community-acquired gastrointestinal disease is unknown.
  
  
  OBJECTIVE
  The objective of this study was to evaluate the capability of a syndromic surveillance system to detect outbreaks of gastrointestinal disease.
  
  
  METHODS
  A retrospective analysis was conducted comparing ambulatory care data from a health plan with a set of 110 gastrointestinal-disease outbreaks identified by the Minnesota Department of Health during 2001-02. Unusual clusters of illness (i.e., signals) in the health-plan data were identified by analyzing daily counts of gastrointestinal illness using an adjusted space-time scan statistic. Concordance was defined as < or =5 km between outbreak and signal and the signal occurring within 1 week of the outbreak.
  
  
  RESULTS
  During 104 weeks, the number of signals was roughly what would have been expected by chance, suggesting that the modeling did a good job of estimating the expected counts of illness and that false alarms would not have occurred much more often than the number predicted at the various thresholds. During the same period, the health department identified 110 eligible gastrointestinal outbreaks. Apparent associations of the three statistically most unusual concordant signals with outbreaks of viral or bacterial gastrointestinal illness were ruled out by the health department on the basis of detailed knowledge of the circumstances and low numbers of affected persons seeking medical care.
  
  
  CONCLUSIONS
  No previously known gastrointestinal outbreaks were identified by this surveillance system. However, relatively few recognized outbreaks resulted in patients seeking medical care, and the sensitivity of this system to detect outbreaks of real significance to public health remains to be determined. Prospective evaluation probably will be required to understand the usefulness of syndromic surveillance systems to enhance existing disease surveillance.
authors.affiliation: Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts 02215, USA. katherine_yih@hphc.org
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Yih
authors.forename: A
authors.initials: A
authors.lastname: Abrams
authors.forename: R
authors.initials: R
authors.lastname: Danila
authors.forename: K
authors.initials: K
authors.lastname: Green
authors.forename: K
authors.initials: K
authors.lastname: Kleinman
authors.forename: M
authors.initials: M
authors.lastname: Kulldorff
authors.forename: B
authors.initials: B
authors.lastname: Miller
authors.forename: J
authors.initials: J
authors.lastname: Nordin
authors.forename: R
authors.initials: R
authors.lastname: Platt
mesh_terms: D000553:Ambulatory Care; D004196:Disease Outbreaks / Q000517:prevention & control*; D015991:Epidemiologic Measurements; D005767:Gastrointestinal Diseases / Q000453:epidemiology* / Q000517:prevention & control; D006801:Humans; D008910:Minnesota / Q000453:epidemiology; D011159:Population Surveillance / Q000379:methods*; D040442:Public Health Informatics / Q000295:instrumentation*; D012189:Retrospective Studies