The U.S. government is gearing up for the potential arrival of bird flu as concerns grow that it could soon show up on U.S. shores with migrating birds. Meanwhile researchers are learning how infectious diseases, such as a human form of bird flu, might spread by studying how money migrates.
Thanks to the website www.wheresgeorge.com¾ which traces the travels of money around the country and around the world ¾ University of California, Santa Barbara researcher Lars Hufnagel has developed a model of how infectious diseases spread locally, from person to person, as well as from city to city.
"We've quantified how humans move around within the country, so we can combine it with this local infection dynamics and then generate predictions how an infection will, will spread within the United States," says Hufnagel, a post-doctoral fellow at the Kavli Institute for Theoritcal Physics at UCSB.
Hufnagel and his colleagues first started studying the spread of disease in order to try to understand how the SARS epidemic spread in 2000. "The worldwide aviation network is sufficient to explain how SARS spread around the world," he explains. "But it was also clear that if you want to model how epidemics spread on a smaller scale, that you need to incorporate other means of transport, like people driving by car or by bus and train."
Diseases, like money, are transported from place to place by people.
"So we analyzed roughly half a million dollar bills ¾ how they move around the United States," he says.
As reported in the journal "Nature," the researchers found they could describe people's movements using simple math.
"Human travel within the United States can be described by very simple mathematical laws and these laws do not depend on if you live in a small or large city. So they're universal within the United States."
Hufnagel says that his model may not apply to all infectious diseases, but he hopes that it will help public health officials come up with measures to stop the spread of an epidemic in the U.S. and around the globe. The government's proposed response plan assumes a worst-case scenario where as many as 90 million people in the U.S. would become sick.
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