The median outbreak size, as measured by the total number of cases, was 13 with a range of 1 to 134 cases (Table 3, Figure 2c ). There were approximately equal proportions of small (total number of cases less than 5) and large (total over 20) outbreaks ( Table 2 ). Outbreaks that remained in the community involved a median of 2 cases, while those that were hospital based involved a median of 20 cases and those that were mixed had a median of 22 cases (Table 3) . Outbreaks tended to be smaller when the index case was typical versus atypical or hemorrhagic (median number of cases 2 vs. 27 vs. 16.5) and when the index case was identified (median number of cases 3 vs. 27.5) ( Table 3 ). The outbreak size was similarly small across all 3 settings when the index case was identified and similarly large across the settings when it was not.