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Wednesday, January 25, 2006


Dave Drasha

Scientists trace dollar bills for clues to predict pandemics

Last Updated Wed, 25 Jan 2006 13:55:10 EST [30]CBC News

An internet site that tracks the travels of U.S. dollar bills is
helping scientists predict how viruses may spread in a pandemic.

The rapid spread of SARS (severe acute respiratory syndrome) in 2003
showed how air travel can unleash viruses worldwide in hours. In
comparison, the Black Death spread about two kilometres a day in the
Middle Ages, giving communities more time to evacuate or try to

llustration symbolizes the geographic movement of a single dollar bill
from either Seattle (blue) or New York (yellow) to various
destinations in the U.S. (Courtesy: UCSB and the Max Planck Institute
for Dynamics and Self Organization)

Researchers are looking for ways to model where and when people move
during a pandemic.

It's hoped that by identifying, treating and isolating people
potentially exposed to a pathogen, that pandemics can be prevented or
controlled better.

But since people don't wear tracking devices, German and American
physicists turned to the internet site Where's George to get an idea
about how people travel.

The website allows volunteers to record the serial number of a U.S.
dollar bill and follow its movements around the country for fun. About
50 million banknotes are registered on the site. (One Canadian
equivalent, called Where's Willy, traces five-dollar bills.)

Lars Hufnagel, a postdoctoral researcher at the University of
California in Santa Barbara, and his colleagues found the majority of
bills (52 to 71 per cent) moved less than 10 kilometres in two weeks.

Banknotes are mainly dispersed in a series of random steps over short
distances, with occasional hops over long distances, the team
concludes in Thursday's issue of the journal Nature.

The findings challenge a traditional model of epidemiology that
suggests viruses disperse like waves, moving in phases over
geographical areas, the way dust particles spread on the surface of

"We are optimistic that this will drastically improve predictions
about the geographical spread of epidemics," said study author Theo
Geisel, director of the Max Planck Institute for Dynamics and
Self-Organization in Gattingen, Germany.



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