This is pretty cool. It turns out that by aggregating daily search numbers for certain influenze-related terms, google can track regional flu activity about as well as the CDC (see chart below). It's all part of googles Predict and Prevent initiative. The coolest part, is that googles data is available essentially in real time, while the CDC data takes two weeks to gather and compile.
So, watch google flu trends to see when the flu hits your area. You'll be reading about it from the CDC about two weeks later.