Figure 1
From: Enhancing disease surveillance with novel data streams: challenges and opportunities
The link between public health problems and NDS is modified by user behavior (i.e., propensity to search, what terms are chosen to search, etc.), user demographics, external forces on user behavior (i.e., changing disease severity, changing press coverage, etc.), and finally by public health interventions, which by design aim to modify the public health problem creating feedback loops on the link to NDS.