Canadian researchers, back in 2006, called it Infodemiology — using volume and locations of Internet searches to track influenza outbreaks. Dr. Gunther Eysenbach’s paper notes that:
The “Google ad sentinel method” proved to be more timely, more accurate and – with a total cost of Can$365.64 for the entire flu-season – considerably cheaper than the traditional method of reports on influenza-like illnesses observed in clinics by sentinel physicians.
Now, Google makes this disease-tracking information available directly to the public. The New York Times this month reports that Google uses searches to track flu’s spread. Google’s new service, Google Flu Trends, aggregates data from user searches to create national and state-by-state charts showing levels of interest in a variety of flu-related terms, such as “muscle aches” and “chest congestion.” A comparison of historical data from the CDC and past years’ Google searches shows a correlation between the two, with Google data actually showing the trends two weeks before the CDC data.
via David Rothman