How Google could predict the spread of the winter flu?
Google could predict the spread of the winter flu in the United States, not just nationally, but down to specific regions and even states. The company could achieve this by looking at what people were searching for on the Internet. Since Google receives more than three billion search queries every day and saves them all, it had plenty of data to work with.
Google took the 50 million most common search terms that Americans type and compared the list with CDC data on the spread of seasonal flu between 2003 and 2008.
Others had tried to do this with Internet search, but no one else has as much data, processing power, and statistical know-how as Google.