"We were confident that we could learn a lot from the data collected at the www.wheresgeorge.com bill-tracking website, but the results turned out far beyond our expectations," said Lars Hufnagel, a post-doctoral fellow at the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara and co-author of an article describing the research in the January 26 issue of the journal Nature.
The worldwide spread of disease particularly pandemics with disastrous consequences for human health and economics has become a serious threat in the globalized world of intense international trade and travel. The threat of bird flu, the possible emergence of a new human "supervirus," and the potential of a worldwide flu pandemic, make predicting the spread of these diseases more urgent than ever.
Historical pandemics, like the 14th-century plague, moved slowly in waves across geographical areas, because in the Middle Ages people could typically only travel a few kilometers a day. The speed with which epidemics could spread was thus kept in check. It took the plague three years to move up the European continent, south to north, with an average rate of spread of about two kilometers a day.
"But today people move great distances in short time periods, as well as short distances, and they use variable means of transportation," said Hufnagel. "Thus we can expect that future pandemics will spread according to other rules, and more quickly. The rapid worldwide spread of SARS (severe acute respiratory syndrome) has already demonstrated this."