Comparison of ILI incidence according to different definitions of ILI with the HPA's estimated ILI cases [17,21,27,28]. As in Fig 3, the denominator used is those participants who completed the symptoms questionnaire on the week in question. All curves are plotted using a 3-week moving average; plots without this moving average can be found in the Supplementary material.
Tilston et al. BMC Public Health 2010 10:650 doi:10.1186/1471-2458-10-650