title: Use of the local Knox statistic for the prospective monitoring of disease occurrences in space and time.
abstract: The detection of clusters of events occurring close together both temporally and spatially is important in finding outbreaks of disease within a geographic region. The Knox statistic is often used in epidemiology to test for space-time clustering retrospectively. For quicker detection of epidemics, prospective methods should be used in which observed events in space and time are assessed as they are recorded. The cumulative sum (CUSUM) surveillance method for monitoring the local Knox statistic tests for space-time clustering each time there is an incoming observation. We consider the design of this control chart by determining the in-control average run length (ARL) performance of the CUSUM chart for different space and time closeness thresholds as well as for different control limit values. We also explain the effect of population density and region shape on the in-control ARL and discuss other distributional issues that should be considered when implementing this method.
authors.affiliation: Department of Statistics, Virginia Tech, Blacksburg, VA 24061-0439, USA. jemarsh2@vt.edu
authors.forename: J
authors.initials: J
authors.lastname: Brooke Marshall
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Spitzner
authors.forename: William H
authors.initials: WH
authors.lastname: Woodall
mesh_terms: D003198:Computer Simulation; D004196:Disease Outbreaks; D004812:Epidemiologic Methods; D006801:Humans; D011634:Public Health / Q000379:methods*; D013029:Space-Time Clustering