Correlation between population density and the frequency of Creutzfeldt-Jakob disease in France.

Epidemiologic studies of Creutzfeldt-Jakob disease (CJD) in countries throughout the world have consistently shown higher urban than national disease frequencies, but this finding has usually been ascribed to case-finding artefact. A detailed analysis has now been completed of annual mortality rates of CJD in France, based on a systematic study of 255 consecutive cases dying during the period 1968-1980, of whom 85 resided in the paris metropolitan area. In the country as a whole, the frequency of CJD increased from rural, through urban, to the Paris region; and in the Paris region, the frequency increased from the lowest to the highest density areas. The magnitude of this positive correlation between population density and the frequency of CJD is not explained by differences in age distribution of the various population groups, and suggests a role for random inter-human spread, either direct or indirect, in natural disease transmission.