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Table 4 Characteristics of the daily number of respiratory syndrome or influenza-like illness cases during baseline and the test period (week 36 to week 52, 2009), test statistics on the probability distribution of daily counts, the identification of day-of-the-week effects, and Poisson CUSUM parameters during individual baseline periods

From: Validity and timeliness of syndromic influenza surveillance during the autumn/winter wave of A (H1N1) influenza 2009: results of emergency medical dispatch, ambulance and emergency department data from three European regions

  EMD-AT EP-AT EP-BE ED-BE ED-ES
Respiratory syndrome ILI ILI ILI ILI
Period Baseline* Test Baseline* Test Baseline* Test Baseline* Test Baseline* Test
Mean daily count 4.7 4.8 0.07 0.2 4.2 5.0 13.6 17.9 4.1 7.3
  Standard deviation 2.2 2.1 0.3 0.5 2.1 2.5 4.0 6.0 3.0 8.0
  95% Confidence Interval 4.6-4.9 4.4-5.5 0.05-0.09 0.2-0.3 3.9-4.5 4.5-5.4 13.0-14.2 16.8-19.0 3.3-4.9 5.9-8.7
Median daily count 5 5 0 0 4 5 13 18 3 5
Minimum daily count 0 1 0 0 0 1 5 5 0 0
Maximum daily count 15 12 2 2 10 14 27 34 15 36
Day-of-the-week effect yes   no   no   no   yes  
evaluated by Kruskal-Wallis test p = 0.007   p = 0.43   p = 0.70   p = 0.19   p = 0.04
Mean daily count           
  Monday 4.7   0.08   4.1   14.6   2.7  
  Tuesday 4.4   0.08   4.0   12.3   4.9  
  Wednesday 4.4   0.03   3.9   12.5   5.5  
  Thursday 5.0   0.08   3.6   13.7   4.8  
  Friday 4.5   0.12   4.8   14.6   3.4  
  Saturday 4.7   0.08   4.3   13.2   5.5  
  Sunday 5.4   0.05   4.6   14.4   2.0  
Poisson CUSUM calibration $           
no day-of-the-week variation    mean = 0.07   mean = 4.2   mean = 13.6    
k = 1   k = 5   k =14
S0 = 1   S0 = 4   S0 = 10
h = 2   h = 7   h = 20
day-of-the-week variation           
  stratum 1 Sunday         Sunday, Monday  
mean = 5.4         mean = 2.3  
k = 6          
S0 = 5         k = 3  
h = 10         S0 = 3  
         h = 5  
  stratum 2 Monday-Saturday         Tuesday-Saturday  
mean = 4.6         mean = 4.8  
k = 5         k = 5  
S0 = 4         S0 = 4  
  h = 7         h = 7  
  1. *baseline = baseline period for Poisson CUSUM calibration: EMD-AT: 1/2005-12/2008 (except December to March); EP-AT: 1/2006-12/2008 (except November to March); EP-BE: 3/2009-8/2009); ED-BE: 3/2009-8/2009; ED-ES: 3/2009-8/2009.
  2. test = test period for validity and timeliness assessment; covers the autumn winter wave of pandemic A(H1N1) influenza in 2009 (week 36/2009 to week 52/2009).
  3. $Poisson CUSUM calibration: mean = baseline mean; k = reference value; S0 = head start value; h = threshold value.