Figure 1
From: Timeliness of syndromic influenza surveillance through work and school absenteeism
Curve of the weekly influenza-like-illness (ILI) incidence per 100,000 inhabitants (right axis) and scatter plots with smoothed curves of the daily absenteeism rates (left axis) for (a) SNCB/NMBS and MEDEX worker data, (b) nursery school, (c) primary school and (d) secondary school data by community (Flemish, French and German-speaking) during the A(H1N1)2009 epidemic in Belgium. The straight horizontal lines indicate the ILI threshold and the gray areas indicate school holiday periods. * For the French Community, data for nursery and primary school are not available separately and are only presented in graph (b).