Fig. 3From: Reconstructing the household transmission of influenza in the suburbs of Tokyo based on clinical casesPartial serial interval histograms of the crude number of secondary cases. Only the left side of the histograms (≤ 2 days) is shown. In the type A histogram, there is a downward trend up to 0.5 days; in the type B histogram, there is a downward trend up to 1.25 days (type B). These may be attributable to simultaneous infections outside the householdBack to article page