In order to obtain a robust estimate of the time taken for case numbers to reach those observed on 29 May, we considered values of the reproduction number ranging from 1.2 to 1.8 and mean serial interval from 2 to 4 days, consistent with other estimates of the mean serial interval of pandemic H1N1 of 1.9 days [20], 2.8 days [12, 16, 21] , 3.2 days [22] and longer [23] . We performed 1000 simulations for each pair of values, and recorded the mean and standard deviation over these simulations.