Analysis of the geographical distribution of sporadic Creutzfeldt-Jakob disease in France between 1992 and 1998.

BACKGROUND Creutzfeldt-Jakob disease (CJD) is a rare fatal dementia caused by a transmissible agent. However, the mechanism leading to the disease is unknown in the majority of cases. The presence of geographically clustered cases might indicate a common environmental exposure to the transmissible agent, or case-to-case transmission of the agent. This study sought evidence of clustering of cases of sporadic CJD in France. METHODS A total of 402 individuals who died from definite or probable sporadic CJD in France between 1992 and 1998 were analysed. The geographical distribution of cases was analysed using three different clustering methods. An analysis of the distribution of the distances between pairs was performed to look for evidence of clustering. Then, two methods of cluster detection were used to identify the locations of clusters. RESULTS Each of our analyses found some evidence of clustering, though the extent of that clustering differed between approaches. The strongest evidence, statistically, related to three cases living in a small rural area in South-West France (P = 0.001). Two of the three cases lived in the same area throughout life. They had also both undergone surgery on several occasions. Little information is available on the third case. CONCLUSION Some sporadic CJD cases in France may be aetiologically linked. There was strong evidence that three cases in South-West France formed a cluster but the precise mechanism underlying this cluster of cases remains unclear. The potentially long incubation period of the disease makes the identification of links between such cases difficult.