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Comparison of the proportions of index cases and positive contacts by age group.
Proportions represent the total number of individuals in each sample that belong to each age group, as a proportion of the total sample size, and are plotted in percentages above each bar. The proportions were statistically compared using two-sample z-tests. Statistical significance is indicated above the error bars: p > 0.05 (ns), p < 0.05 (*), p < 0.01 (**), p < 0.001 (***), p < 0.0001 (****).
