Fig. 2.

Number and order of interval censored infections by serotype. For each serotype the number of interval-censored infections are plotted against year. Note that for comparison purposes the scale of the y axis is not the same in each panel. Per individual, these infections are broken down by which infection they constitute (primary, secondary, tertiary, or quaternary). Because both DENV-1 and DENV-2 cocirculated before the beginning of the study period, the majority of individuals were already exposed to at least one of these serotypes and thus most interval-censored infections were not primary infections. For this same reason (the cocirculation of DENV-1 and DENV-2 before 1999), there are considerably fewer DENV-1 and DENV-2 interval-censored infections than DENV-3 and DENV-4 interval-censored infections.