Disease trackers follow the dollars

LOS ANGELES – Scientists think they may have found a better way to predict how diseases like a global flu epidemic could spread: Follow the money.

Using the popular “Where’s George?” Web site that tracks U.S. dollars, researchers developed a mathematical tool that could help chart the path of an infectious disease.

Details appear in today’s issue of the journal Nature.

Fears of a global flu epidemic have arisen from the spread of bird flu. Experts have warned that if it ultimately begins spreading among people, travelers are the most likely way it will become a worldwide threat.

Tracking travelers is difficult, so researchers came up with the idea of studying them indirectly by tracing how money circulates through the economy.

In the study, scientists traced the whereabouts of nearly half a million dollar bills on www.wheresgeorge.com, a bill-tracking site.

Users register their money and then spend it. They can monitor the money’s movement online as it changes hands.

Researchers found that most of the money (57 percent) traveled between 30 miles and 500 miles over about nine months in the United States. About a quarter of the bills moved more than 500 miles.

By analyzing the movement of money – and human travel – over different distances, the scientists found that the money followed a predictable pattern. The method could be used to create more realistic disease models that track the spread of germs and perhaps prevent outbreaks, they say.