At a constant alert rate of 1% for all methods, the sensitivity for detecting additional counts was calculated by performing the following steps: 1) running the algorithm to determine expected values and SDs for each facilitysyndrome-day; 2) fi nding the 99th percentile cutoff value for the test statistic for each dataset-algorithm-mean count category as explained above; 3) for each facility-syndrome day, determining whether the observed count plus additional counts is greater than or equal to the threshold value (threshold value = expected value + SD × 99th percentile cutoff value); and 4) calculating sensitivity as the percentage of days on which the additional counts would exceed the threshold value and therefore be detected. Using this method, a single computer run can calculate sensitivity for detecting single-day additional counts on all days in the dataset; if the additional counts are spread over multiple days, separate computer runs would be needed (7).