Find out the flu outbreak in US

Google Flu Trends uses aggregated Google search data to estimate flu activity in your state up to two weeks faster than traditional flu surveillance systems.
Google have found a close relationship between how many people search for flu-related topics and how many people actually have flu symptoms. Of course, not every person who searches for "flu" is actually sick, but a pattern emerges when all the flu-related search queries from each state and region are added together. Google compared their query counts with data from a surveillance system managed by the U.S. Centers for Disease Control and Prevention (CDC) and found that some search queries tend to be popular exactly when flu season is happening. By counting how often Google see these search queries, Google can estimate how much flu is circulating in various regions of the United States.

http://www.google.org/flutrends/