Summary: 843 Am J Epidemiol 2003;157:843854
American Journal of Epidemiology
Copyright © 2003 by the Johns Hopkins Bloomberg School of Public Health
All rights reserved
Vol. 157, No. 9
Printed in U.S.A.
PRACTICE OF EPIDEMIOLOGYPRACTICE OF EPIDEMIOLOGY
Identifying West Nile Virus Risk Areas: The Dynamic Continuous-Area Space-Time
Constandinos N. Theophilides1, Sean C. Ahearn1, Sue Grady1, and Mario Merlino2
1 Center for Advanced Research of Spatial Information, Hunter College, City University of New York, New York, NY.
2 Office of Policy and Planning, New York City Department of Health and Mental Hygiene, New York, NY.
Received for publication May 31, 2002; accepted for publication December 20, 2002.
The Dynamic Continuous-Area Space-Time (DYCAST) system was developed to identify and prospectively
monitor high-risk areas for West Nile virus in New York, New York (New York City). The system is based on a
geographic model that uses a localized Knox test to capture the nonrandom space-time interaction of dead birds,
as an indicator of an intense West Nile virus amplification cycle, within a 1.5-mile (2.41-km) buffer area and 21-
day moving window. The Knox analysis is implemented as an interpolation function to create a surface of
probabilities over a grid of 1,400 cells overlaying New York City. The model's parameters were calibrated using