Major events in digital public health surveillance. Abbreviations: GFT: Google Flu Trends, GDT: Google Dengue Trends. ProMED-mail (69), de Grote Griepmeting (63), Web page views used for flu surveillance (59), Google ad click rate used for surveillance (41), HealthMap (20), H1N1 missed by GFT (31), FluNearYou (102), GFT overestimates (77), FluSight (6), GFT and GDT no longer available (2).