Brain Advance Access published online on November 28, 2008
Brain, doi:10.1093/brain/awn303
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Enhanced geographically restricted surveillance simulates sporadic Creutzfeldt-Jakob disease cluster
1Australian National Creutzfeldt-Jakob Disease Registry, Department of Pathology, The University of Melbourne, Parkville, Victoria, 2National Centre in HIV Epidemiology and Clinical Research, The University of New South Wales, Sydney, New South Wales, 3North Sydney and Central Coast Area Health, New South Wales, 4The University of Newcastle, Newcastle, New South Wales and 5The Mental Health Research Institute of Victoria, Parkville, Victoria, Australia
Correspondence to:
Steven J. Collins, Department of Pathology, The University of Melbourne, Victoria 3010, Australia E-mail: stevenjc{at}unimelb.edu.au
Spatio-temporal clustering of sporadic Creutzfeldt-Jakob disease (sCJD) has been recognized and investigated previously in various global settings including Australia. Generally, despite often extensive investigation, explanations such as point source outbreaks and plausible case-to-case transmission links have not been identified to explain the apparently higher case rates than expected. In the context of national surveillance during the period 1993–2006, an increased number of cases of sCJD were recognized in a circumscribed coastal region of eastern Australia. To assess the significance of this apparent clustering, the Spatial Scan Statistic was used to examine for geographic excess of CJD mortality at spatial and temporal combined, spatial only and temporal only levels. A significant spatial cluster was confirmed, encompassing three contiguous statistical local areas within the state of New South Wales (NSW). Detailed epidemiological analysis did not reveal a plausible cross-over or point source transmission event. Further evaluation prompted the conclusion that vigilant and motivated managing clinicians in this geographically circumscribed area of NSW evinced a sustained higher level of clinical awareness for the broad phenotypic spectrum of CJD with reliable referral of suspect cases for further investigation. In addition, these physicians established and maintained a well-coordinated and active approach to suspect CJD autopsy. This combination of factors translated into a higher intensity of surveillance at approximately twice the rate per population observed in the entire state, culminating in twice the incidence of sCJD at around 2.28 cases/million population/year. The hypothesis that intensity of surveillance for rare disorders can be objectively measured and that this can positively correlate with disease incidence deserves further exploration. It may prove to be an important insight into the varying incidence rates over periods of time within individual nations and between different countries.
Key Words: CJD; cluster analysis; epidemiology; surveillance; incidence
Abbreviations: CJD, Creutzfeldt-Jakob disease; NSW, New South Wales; PRNP, prion protein gene; RRMH, Mantel–Haenszel rate ratio estimate; sCJD, sporadic CJD; SLA, statistical local area
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Received July 29, 2008. Revised October 20, 2008. Accepted October 20, 2008.
*These authors contributed equally to this work.
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