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Syndromic Surveillance for Early Location of Terrorist Incidents Outside
of Residential Areas
Manfred S. Green,1,2 Z. Kaufman1 1Ministry of Health, Tel Aviv, Israel; 2Tel
Aviv University, Tel Aviv, Israel
Corresponding author: Manfred S. Green, Israel Center for Disease Control, Gertner Institute, Sheba Medical Center, Tel Hashomer, Israel 52621. Telephone: 972-3-737-1500; Fax: 972-3-737-1515; E-mail: m.green@icdc.health.gov.il.
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.
Abstract
Introduction: A terrorist attack might occur at places outside of residential areas (e.g., workplace, entertainment venues, or shopping centers). Cluster analysis using available data on residential
addresses alone will not yield the probable place of exposure.
Objectives: The study aimed to facilitate early detection of terrorist incidents in areas outside of residential areas (e.g., workplaces and shopping centers).
Methods: An approach was suggested for estimating the probable location of exposure on the basis of
the distribution of the residential addresses on the assumption that persons tend to live closer to their place of work,
or visit entertainment venues or shopping centers closer to their place of residence than would be expected by chance. A two-stage process of implementing available spatial statistics programs was proposed. In the
first stage, a cluster analysis program was employed by using residential addresses. The
SaTScan™ software, developed at the National Cancer Institute, was used with its space-time permutation model specifically developed for conducting
continuous surveillance. If more than one substantial cluster is identified, a possible incident outside of the residential area was
considered. The mean center and standard deviation are computed for those census tracts included in the substantial clusters to identify the area where the exposure might have occurred. For this task, the CrimeStat
II™ was used, a spatial statistic program originally developed for analysis of crime locations. To narrow potential places of exposure, the cluster analysis should be performed in the first stage by age groups such as infants, children, persons aged
<19 years, the working age category (19--65 years), and older persons (>65 years). Substantial clusters in
the working age category alone could focus the resulting investigation on workplaces. A geographical information system
(GIS) program (ArcGIS™, ESRI™, Redlands, California) was used for geocoding addresses and
for other procedures needed to prepare data for cluster analysis and for presenting the results. This approach was demonstrated through a series of simulations of deliberate dispersion of anthrax spores in a large hospital where residential addresses of all
the staff members were available. Simulated cases among the staff were superimposed on background data of
patient visits to community clinics for influenza-like illness.
Results: A possible place of exposure was identified at a distance of approximately 1 kilometer from the hospital
Conclusion: The combination of multiple spatial statistics tools demonstrates promising capabilities for
identifying terrorist incidents outside of residential areas, even when only residential addresses are available.
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