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Leveraging Syndromic Surveillance During the San Diego Wildfires, 2003

Jeffrey M. Johnson, L. Hicks, C. McClean, M. Ginsberg
San Diego County Health and Human Services Agency, San Diego, California

Corresponding author: Jeffrey M. Johnson, San Diego County Health and Human Services Agency, Community Epidemiology Division, 1700 Pacific Hwy., MS P511C-A, San Diego, CA 92186. Telephone: 619-531-4945; E-mail:

Disclosure of relationship: The contributors of this report have disclosed that they have no financial interest, relationship, affiliation, or other association with any organization that might represent a conflict of interest. In addition, this report does not contain any discussion of unlabeled use of commercial products or products for investigational use.


Introduction: On October 25, 2003, one of the largest fires in California history began in San Diego County. Over a period of three days, the air quality deteriorated to unhealthy and hazardous levels, prompting school cancellations and the general public to stay at home. In response to the fires, smoke, and circulating ash, San Diego County Public Health leveraged existing syndromic surveillance capabilities to assess impact on the county's emergency medical system.

Objectives: This surveillance capability was rapidly deployed to assess the impact of the fires on selected types of emergency department visits.

Methods: In response to the fire, two existing syndromic surveillance data sources were monitored: prehospital paramedic transport chief-complaint data and local over-the-counter (OTC) medication sales data acquired from the National Retail Data Monitor system. In addition, 15 emergency departments reported syndromic surveillance information including asthma, bronchitis, emphysema, or other respiratory symptoms with no fever, eye irritation, smoke inhalation, burns, chest pain, and diarrhea. Daily air-quality data was also acquired. The analytic methods included time-series and process-control charts (e.g., P-Chart, U-Chart, CUSUM, and EWMA).

Results: Information on 31,321 emergency department visits, 8,625 prehospital transports, and OTC data were analyzed. Respiratory indicators demonstrated substantial increases during the days of greatest fire burn and unhealthy air quality, with postfire levels approaching prefire levels when air quality improved. A marked increase in smoke inhalation and eye irritation visits was also observed. No noticeable increase was noted among visits for chest pain or diarrhea. The total number of emergency department visits initially declined during the fire period, which corresponded to the days that students and employees were asked to remain at home. Air quality in San Diego deteriorated substantially during the fires concurrent with substantial increases in asthma- related emergency department visits and increases in local OTC sales of bronchial remedies, cold/cough syrup, and nasal products.

Conclusion: Existing syndromic surveillance capabilities were used to monitor the immediate impact of the wildfires in San Diego County. These results demonstrated a real impact on selected medical services. Certain fire-related outcomes were expected, especially related to asthma and other respiratory health outcomes and increased sales of selected OTC products. In retrospect, this disaster served as an "outbreak," validating the importance of syndromic surveillance as a dual-use tool and highlighting the need for system flexibility. Syndromic surveillance is a useful tool during a natural disaster, assisting future disaster preparations and generating hypotheses for long-term follow-up studies.

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Date last reviewed: 8/5/2005


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