This has already been written up by the MSM (such as this article), so I’ll just quote a bit from them:
Circulation of money may predict pandemics
A popular U.S. Web site that tracks the geographical circulation of money could offer new insights into predicting the spread of infectious diseases like bird flu.
Money, like diseases, is carried by people around the world, so what better way to plot the spread of a potential influenza pandemic than to track the circulation of dollar bills, researchers reasoned.
Researchers in Germany and the United States did just that to develop a mathematical model of human travel that can be used to plot the spread of future pandemics.
To model transmission, they used data from the Where’s George website, where people can enter their location and bill serial numbers to track them around the country. It’s obviously not a perfect model–there will be some bias as to who enters their money, so some areas may show up more frequently than others–but it’s a neat trick and a novel way to use that information.
You can find the original article here.