Figure 2

Basic approach to anomaly detection. The basic approach to anomaly detection uses a 7 day test period (days -3 to -9) as background data, days -1 to -2 as a buffer period and day 0 'test day' as the test period. Data shown are the raw daily A(H1N1) document frequencies found by BioCaster for United States. ProMED-mail alerts are shown by vertical grey lines.