There is a remarkable relationship between actual epidemiologic data and flu oriented google searches. Actual epedemiologic data is collected by health institutions and is based on actual reports of the number of afflicted people. Similarily, when more people are sick then they also want to be informed about their disease. Looking for medical information on the internet has become almost a natural reflex for many people. As they look for information google can bundle those searches based on selected key words related to flu.
When charted out these two graphs – the epedemiologic data and the google searches – share mostly the same trends and characteristics.
Bottom line: Google flu trends can be a valuable tool in tracking epidemiology outbreaks. In the future this concept will definitively be expanded to other disease areas.