The surveillance period was spread over 134 weeks from week 1 of 2009 to week 29 of 2011. For the two historical methods, expected numbers of all consultations were calculated during these 134 weeks, using a training period of at least 3 years. A 95% confidence interval was calculated for each weekly expected number. A weekly count observed was considered significantly greater than the expected value if it was above the 95% upper confidence limit.