Table 1 Description of alarm strategies for the detection of spatial clustering.

N > 95^th percentile

Number of ED respiratory visits is too high

N > 95^th percentile, by season

Number of visits is too high, separate values by season

M > 95^th percentile

M statistic is too high

M > 95^th percentile, by season

M statistic is too high, separate values for each season

MN > 95^th percentile

Calculate M × N, value is too high

N and MN rules

N is too high (top 0.5% distribution)

Or M × N is too high (top 0.5% distribution)

Or both N is high (>80%) and M × N is high (>80%)