Si=max(0,???Si???1+(Xi?????)???k).In this formula Xi denotes the observed daily count on day i, ?? denotes the overall mean daily count estimated from the data, and k is an off-set parameter set by the user.8,9 The algorithm alarms or flags whenever Si exceeds a value h, where h is computed empirically to guarantee a user-defined false positive rate in the non-flu season.The CUSUM based on deviati