Our team found that certain aggregated search queries tend to be very common during flu season each year. We compared these aggregated queries against data provided by the U.S. Centers for Disease Control and Prevention (CDC), and we found that there's a very close relationship between the frequency of these search queries and the number of people who are experiencing flu-like symptoms each week. As a result, if we tally each day's flu-related search queries, we can estimate how many people have a flu-like illness.
Despite the fact that this tool is 5 months old, it's been helpful to compare activity to hysteria. Possibly not the most rigorous methodology out there, but an interesting way to capture "on-the-ground" thinking. However, based on the current status of the swine flu, it's nice to visualize the difference between panic and events.
They have also just built an experimental model for Mexico as well.