SURVEILLANCE DATA FOR WATERBORNE ILLNESS DETECTION - AN ASSESSMENT FOLLOWING A MASSIVE WATERBORNE OUTBREAK OF CRYPTOSPORIDIUM INFECTION

Following the 1993 Milwaukee cryptosporidiosis outbreak, we examined d ata from eight sources available during the time of the outbreak. Alth ough there was a remarkable temporal correspondence of surveillance pe aks, the most timely data involved use of systems in which personnel w ith existing close ties to public health programmes perceived the impo rtance of providing information despite workload constraints associate d with an outbreak. During the investigation, surveillance systems whi ch could be easily linked with laboratory data, were flexible in addin g new variables, and which demonstrated low baseline variability were most useful. Geographically fixed nursing home residents served as an ideal population with non-confounded exposures. Use of surrogate measu rements of morbidity can trigger worthwhile public health responses in advance of laboratory-confirmed diagnosis and help reduce total morbi dity associated with an outbreak. This report describes the relative s trengths and weaknesses of these surveillance methods for community-wi de waterborne illness detection and their application in outbreak deci sion making.