[Clips] Banknote tracking helps model spread of disease

R. A. Hettinga rah at shipwright.com
Thu Jan 26 09:38:55 PST 2006


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  Date: Thu, 26 Jan 2006 12:02:32 -0500
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  From: "R. A. Hettinga" <rah at shipwright.com>
  Subject: [Clips] Banknote tracking helps model spread of disease
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  <http://www.newscientist.com/article.ns?id=dn8636&print=true>

  New Scientist


  Banknote tracking helps model spread of disease

  	*	18:15 25 January 2006
  	*	NewScientist.com news service
  	*	Will Knight

  Tracking the movements of hundreds of thousands of banknotes across the US
  could provide scientists with a vital new tool to help combat the spread of
  deadly infectious diseases like bird flu.

  Modern transport has transformed the speed at which epidemics can spread,
  enabling disease to rip through populations and leap across continents at
  frightening speed.

  However, scientists possess few mathematical models to help them understand
  these movements and how this might govern the global spread of disease. To
  a large degree, this is because tracking the movements of so many people
  over such a large area is next to impossible.

  But now physicists from the Max Planck Institute in Gvttingen, Germany, and
  the University of Santa Barbara, California, US, have developed a model to
  explain these movements, based on the tracked movements of US banknotes.

  Dirk Brockmann and colleagues used an online project called
  www.wheresgeorge.com (George Washington's image is on the $1 bill) to track
  the movements of dollar bills by serial number. Visitors to the site enter
  the serial number of banknotes in their possession and can see where else
  the note may have been.

  The team tracked 464,670 dollar bills across the US using 1,033,095
  individual reports. The fact the notes are carried by people suggests it is
  a good way of modelling other things that people may carry, including
  disease.

  Piggy bank

  The researchers noticed that the bills' move according to two mathematical
  rules, each known as a power law. One describes the distance travelled in
  each step of the journey, the other the length of time spent between
  journeys.

  While most notes travel a short distance each time, there is a slim
  probability that it will leap a very long distance - perhaps carried from
  one side of the US to the other in the wallet of a passenger taking a
  flight. Secondly, while some notes move on quickly, there is a fair chance
  that it will remain in one place for a long period - for instance stuffed
  into a child's piggy bank.

  Although the movements of individual bills remain unpredictable, the
  mathematical rules make it possible to calculate the probability that a
  bill will have travelled a certain distance over a certain amount of time.
  "What's triggering this is our behaviour," Brockmann told New Scientist.
  "That is what you need if you want to build quantitative models for the
  spread of disease."

  Very, very important

  Brockmann admits that the movement of money may not perfectly mirror that
  of people. For one thing, he says, it may be that only certain types of
  people are interested in seeing where their bills have been and entering
  that on www.wheresgeorge.com. However, he says comparing the model to
  publicly available information on passenger flights and road travel
  suggests that it is accurate.

  Luis Amaral at Northwestern University, US, believes the study could indeed
  prove very useful to epidemiologists. "Understanding the way people move
  can be very, very important for developing strategies for fighting
  disease," he told New Scientist. "It seems like a very cool study."

  But Amaral also says that the comparison between banknotes and disease is
  far from perfect. "Banknotes do not reproduce like a disease," he notes.


  --
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  R. A. Hettinga <mailto: rah at ibuc.com>
  The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
  44 Farquhar Street, Boston, MA 02131 USA
  "... however it may deserve respect for its usefulness and antiquity,
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-- 
-----------------
R. A. Hettinga <mailto: rah at ibuc.com>
The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
44 Farquhar Street, Boston, MA 02131 USA
"... however it may deserve respect for its usefulness and antiquity,
[predicting the end of the world] has not been found agreeable to
experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'





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