RESPONDING TO REPORTED CLUSTERS OF COMMON DISEASES - THE CASE OF MULTIPLE-SCLEROSIS

Reports of disease clustering are becoming ever more common, and there is increasing pressure on public health agencies to respond idly and appropriately to these reports. We investigate a cluster of five cases of MS occurring in a small multidisciplinary hospital department. Dat a were collected by a variety of methods, including measurement and de scription of the workplace, completion of survey instruments by depart ment staff, construction of case histories of persons with MS. The res ults indicated that the department comprised a high-risk population an d that only one case of MS could have any possible etiologic significa nce. Investigators should consider a number of factors when evaluating disease clusters, including the accuracy of diagnosis, the induction period and cause of the disease, and possible biases in population at risk. Additionally, boundaries should not encircle the cases that led to identification of the cluster and should reflect environmental sign ificance.