Technique for Rapid Detection and Localization of Attacks with Biologic Agents

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Technique for Rapid Detection and Localization of Attacks with Biologic Agents*

Ronald Hoffeld, L. Candell
Massachusetts Institute of Technology Lincoln Laboratory, Lexington, Massachusetts

Corresponding author: Ronald Hoffeld, MIT Lincoln Laboratory, 244 Wood St., Lexington, MA 02420. Telephone: 781-981-2785; Fax: 781-981-6873; E-mail: hoffeld@ll.mit.edu.

Abstract

Introduction: A technique is presented for simultaneously detecting, localizing, and estimating time of attacks with biologic agents or other infectious sources that have a distinct spatial-temporal point pattern. The proposed technique uses high-quality individual location histories coupled with self-reported health status to search for areas where a high density of currently ill persons had congregated in the past. The increased infection rate associated with this detection is indicative of a possible infectious outbreak.

Objective: The system, named BACTrack (Biological Attack Correlation Tracker), was assessed through simulation and analysis to determine achievable sensitivity relative to attack size, infection rate, and participating population.

Method: A sample cohort of the general population was simulated to continuously record their location histories and to report the onset of illness. Developments in location-based cellular phone services enable simplified automation of these functions. Detection was performed by dividing the surveillance area into space-time regions, determining the ratio of ill persons to total population within each region, and flagging regions that exceeded an adaptive threshold on the basis of the statistical variation of the background illness.

Results: A Bacillus anthracis attack affecting 1,100 persons in a city of 150,000 population was simulated. Detection, location, and time of attack were determined with 90% probability 1.5 days after appearance of initial symptoms. The simulation was conducted with health status data with that reflected only whether the person was healthy or ill.

Conclusion: The results demonstrate an ability to operate on poor-quality symptom information. Early detection is made possible by using early diffuse symptoms, efficient data collection, and the signal-processing gain that results from performing location correlation at the time of the attack.

* This work was sponsored under Air Force Contract F19628-00-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the United States Air Force.

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