Increasing the Specificity of Syndromic Data Queries to Investigate Food and Water-Borne Illness Complaints in HoustonOlushola Adeleye, MD, MPH. 1, Mary Carvalho, MPH. 1, Melissa Halm, MPH. 1, Anthony Eshofonie, MD, MPH. 1, Arnulfo C. Rosario Jr., MD, MPH 2, Debo Awosika-Olumo, MD, MS, MPH 1. 1 Bureau of Epidemiology and

2Information Systems Bureau, Office of Surveillance and Public Health Preparedness, Houston Department of Health and Human Services

ObjectiveTo improve the specificity of syndromic surveillance data queries for gastro-intestinal illness caused by a water or food-borne illness.

BackgroundIn February of 2007, the Bureau of Epidemiology (BOE) received a request from Houston Department of Public Works to investigate a possible rise in GI illness associated with complaints about poor water quality in a Northeastern Houston neighborhood. To investigate this complaint, BOE utilized syndromic data from our Real-Time Outbreak Disease Surveillance (RODS).

The initial investigation raised concern about the specificity of the definition used for Gastro-Intestinal complaints in the RODS system for food-borne or water-borne infectious disease. This project built on the original investigation to develop a more specific query for water and food borne illness causing gastro-intestinal illness.

Methods

To investigate the specificity of query result for gastro-intestinal complaints associated with an infectious agent, RODS data were queried for:●Standard GI definition: Any ER chief complaint that states pain, cramps, distension or swelling anywhere in the abdomen, nausea, vomiting, or diarrhea. ●Abdominal pain●Nausea and vomiting●Diarrhea

The queried complaints were:●Graphed by week and age category●Aggregated and mapped to the home zipcode using ArcGIS 9.1.

Data Source: Houston RODS: Collects and synthesizes real-time chief complaint data from 34 area hospitals and health facilities, representing approximately 70% coverage of licensed Emergency Department (ED) beds in the Houston area.

Figure 3a, 3b, 4a and 4b: A comparison of GI complaints as used for the initial investigation and a query of Diarrheal complaints for the same time period (October 2006 through March 2007) by area and by age category

Summary and Conclusion

The gastro-intestinal syndrome category in the RODS system encompasses a large range of complaints, that show large variations throughout the year. This broad spectrum of complaints often makes it difficult to identify increases in ED visits associated with cluster of gastrointestinal illness associated with an infectious agent. Querying Houston’s syndromic data for Diarrheal complaints resulted in count of ED visits that showed less variation throughout the year and increased only during a known period of norovirus outbreaks in Houston. This result suggests that a query for diarrheal complaints, may be a highly specific indicator of outbreaks or clusters of infectious gastrointestinal illness.

The rise in GI illness in Houston’s case report and syndromic data during the time period of interest can be attributed primarily to a spike in illness in children under 4 years of age. These increases were not replicated in Northeast Houston where the water complaints originated.

Maps of both GI and Diarrheal complaints showed similar spatial patterns. There were low levels of illness in the Northeastern Houston area during the time period of interest.

While initially designed as an early event detection system, syndromic data has proven to be a rich data source for supporting case reporting in the City of Houston, Bureau of Epidemiology.

AcknowledgementsDr. Jeremy Espino of General Biodefense

University of Pittsburg RODS Laboratory

GIS Department, HDHHS

Figure 5a and 5b: A comparison of Gastrointestinal complaints and Diarrheal ED complaints by zipcode of home address from January – March 2007.

VARIATIONS ON GASTROINTESTINAL COMPLAINTS: RODS ED DATA

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Figure 2: GI Illness ED visits in RODS. Variations on Gastrointestinal Illness were graphed to identify the most specific query for gastro-intestinal illness associated with diarrhea, nausea and/or vomiting. Diarrheal complaint counts were highly consistent throughout the year with the exception of the ’07 winter, during a known norovirus outbreak. Given the specificity of this category for the known gastro-intestinal illness outbreak, it was chosen for further analysis.

GI Complaints in Houston and Northeast Houston

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Diarrheal Complaints in Houston and Northeast Houston

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Results

Norovirus Outbreaks

Norovirus Outbreaks