Google is amazing.
CNN Health article: "Google tool uses search terms to detect flu outbreaks"
"If you have a fever, headache and runny nose, you might go to Google and type the words "flu symptoms" to see whether you've come down with influenza.
Google knows that you might do something like that, and it also knows which U.S. state you're in. Now, it's putting that information together in a tool that Google says could detect flu outbreaks faster than traditional systems currently in use."
Google Flu Trends