Google predicts spread of flu using search data | Technology | The Guardian

Google has applied its massive data-collecting power for the first time to prediction of the spread of disease, with the launch of a site that claims to be able to raise the alarm over flu outbreaks up to two weeks in advance of existing public services.
Google Flu Trends takes the general search tracking technology pioneered by Google Trends and applies it specifically to influenza. The firm's engineers claim to have devised a way of analysing millions of individual searches related to the disease that in tests proved to correlate closely with the actual incidence of illness. That gives them the potential ability to predict rises in flu cases - information that could be used by health professionals to warn the public or plan their responses.