The full set of unfiltered ESSENCE alerts at levels of high and moderate significance, applied for 8 syndrome groupings to all medical centers, CBOCs and other facilities sending outpatient and emergency department data, was on average 410 per day (539 per week day). Table 1 illustrates the sharp drop in alerting using filters developed to present only sets of records selected for investigation at each level. Additional results will show the sensitivity of the resultant hierarchical system to documented outbreaks at the various levels.