Thursday, December 12, 2013

Circle model predicts spread of disease ahead - Spiegel Online

The spread of a pandemic across the globe is a complicated process. The swine flu of 2009, for example, had its origin in Mexico. Soon the first infections in the neighboring United States were registered, via Spain and Britain came the H1N1 virus a month later to Western Europe and a month later to Asia and Eastern Europe. The SARS epidemic broke out in China in 2003 – and was still faster in the U.S. than in Korea and Singapore


The two German physicist Dirk Helbing of ETH Zurich and Dirk Brockmann of the Humboldt University Berlin now report in the journal “Science” on a new method for predicting the disease-spreading. Your model is, according to the researchers even to determine from the global Infected numbers on a sheet date the origin of the pathogen.

“If you throw a stone into the water, you can predict is on the lake when achieved in any point of the wave,” said Brockmann. “We asked ourselves: Is the spread of infectious diseases in comparison, much more complex, or does she look just complex?”

The “Science” post now provides an answer that surprised even the researchers: The spread of disease actually resembles a circular wave that produces a stone in the water. You have the distances of places and countries only adjust -. Depending on the flight connections

principle of effective distance

Helbing and Brockmann use in their pandemic model differential equations, which reflect, among other things, the infection rate, the recovery rate of infected people and the transport of the pathogen from airport to airport.

pandemic researchers have known for some time that in modern, highly networked world flight connections about deciding where a pathogen enters as fast. For an influenza virus New York is therefore closer to London than the Scottish Aberdeen. The more people between the two locations daily flying back and forth, the greater the likelihood that a pathogen is transmitted.

visualizing the wave of infection, the researchers first used a normal world map. The video above shows such a pandemic simulation that emanates from Atlanta in the United States. In the next step Brock’s team built the card around: The places were not placed upon the actual distance to the origin of the infection around them, but according to the effective removal of the pathogen. Then lie on this new map locations that are connected by many flights, especially close to each other.

The rearrangement of the cities makes the complex propagation pattern on the world map a simple circular wave – exactly like a stone thrown into the water (see the second video). “Now we understand our models only right,” says Brockmann, who now works for the Robert Koch Institute in Berlin.

The photo gallery shows, among other things, the effective distance to major airports from the perspective of Hamburg. London Heathrow is therefore only minimal further than Frankfurt – these two airports would reach a new pathogens from Hamburg first. Shortly thereafter, he would arrive in Paris and Bangkok.

likely origin determine

disease could go many ways, explains Brockmann. This chance also plays a role. It show, however, that agents always would take the shortest route between two locations – this confirmed comparisons with the data of real pandemics


The model can be exploited and backward: “We can now the most likely origin of an ongoing pandemic or epidemic identify,” said Brockmann. This requires good only successively introduce all airports of the model as Origin and see if the places where the infection wave’ve just reached its maximum, located on a circle around the respective origin around. If so, it is highly probable that this starting point.

“We were with our model confirm the places of origin of swine flu and of EHEC with computer help,” says Brockmann. “There were Mexico and the Uelzen district.”

On a global scale range, say researchers alone the flight connections out to predict the spread of disease. However, to simulate a local epidemic about only in Germany, also would have shorter movements are taken into account – for example, the commuter from county to county. Even on this path travels the pathogen on.

The two physicists hope that their model of the effective distance can be used not only for pandemics, but for other network phenomena -. around the spread of rumors or violence in society

No comments:

Post a Comment