(4)Outbreak from Kosovo, Yugoslavia (1972) broken into two components: Entries 10 and 19 [21] . Footnotes for Table 2 : a Nature of the index cases was not clear from the text (limited information) [27] . b Total number of cases listed as 74, consistent with text [38] and second reference [27] . c Total number of cases listed as 5 [28, 34] ; 6 is listed in World Health Organization Table 23 .4 [21] . d Proportion of hospital acquired cases listed as 0.44 because three nurses infected as a result of household exposure and were setting excluded as hospital contacts [21, 36] . e Total number of cases listed as 1 [37] ; 2 is listed in World Health Organization Table 23 .4 [21] . and another third lasted for only through the second generation. Outbreaks that remained in the community lasted a median of 1 generation, while those that were hospital-based lasted a median of 2 generations and those that were mixed lasted a median of 3 generations (Table  3) . Outbreaks tended to be shorter when the index case was typical compared to atypical or hemorrhagic (median number of generations 1 vs. 3 vs. 2, respectively) and when the index case was identified (median number of generations 1 vs. 3) ( Table 3 ). The duration of hospital outbreaks was not affected by the identification of the index cases, but the duration of mixed and community outbreaks lasted up to 6 and 9 generations, respectively, when index cases were unidentified.