Analysis for space-time clustering of CJD cases, Kentucky, 1988-1997

Creutzfeldt-Jakob Disease (CJD) is a transmissible spongiform encephalopathy of humans. It can be transmitted iatrogenically or inherited as an autosomal dominant trait. However, most cases (85%) of the disease are sporadic, occurring stochastically in approximately one person per million population. In 1996, a new, neuropathologically distinct variant of CJD was recognized in a group of unusually young patients who had apparently been infected by exposure to the agent of bovine spongiform encephalopathy (BSE) via contaminated beef products. This prompted many countries, including the United States, to renew their surveillance for CJD to assess the possibility of other variant cases. Spatiotemporal aggregation of cases may indicate a common source of infection or some other shared risk factor. In order to assess the possibility of variant cases, death certificate data was used to examine the spatiotemporal patterns of CJD mortality in Kentucky over a ten-year period. Space-by-time clustering was assessed using Cluster 3.1 software. The findings of this study produced some evidence for a cluster of six cases in central Kentucky. Overall, however, there was little or no evidence to suggest the occurrence of variant or unconventionally acquired cases.