Google Flu Trends showing the prevalence of flu outbreaks across America. it uses aggregated Google search data to estimate flu activity in your state up to two weeks faster than traditional systems.Flu-related search terms are tracked to estimate when and where the flu happens, with data going back to 2003.
They 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. They compared query counts with data from a surveillance system managed by the U.S. Centers for Disease Control and Prevention (CDC) and discovered that some search queries tend to be popular exactly when flu season is happening. By counting how often we see these search queries, we can estimate how much flu is circulating in various regions of the United States.
The data is tracked by state, so you can check and prepare when the flu starts to pick up in your area.