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Smallpox maliciously released in London would spread to several countries before governments could intervene, a new model predicts.

Imagine that a small group of terrorists deliberately infect themselves with smallpox and then walk around London, spreading it to the populace. How much could the terrible disease proliferate before the world realized something was amiss?

This unsettling question is at the heart of new computer model showing how a bioterrorism attack in one city could quickly become the world's problem. Scientists started off with the hypothetical release of smallpox in London, New York, Paris and other major cities, then simulated how travelers would carry the virus to a host of other countries. Their conclusion: In the best-case scenario, smallpox could spread to two to four nations before doctors managed to diagnose it. Still ahead would lie the monumental task of quarantining the infected, distributing vaccines and tracing the source of the outbreak.

Previous research into bioterrorism have indicated that Western cities, with their protocols and vaccines, are pretty well prepared to handle a biological attack, says Alessandro Vespig­nani, a computer and health-sciences professor at Boston's Northeastern University. But in a paper in this month's Scientific Reports (don't worry, it was vetted for international-security issues), he and his fellow researchers argue that the assumption of local readiness is missing the big picture. "The problem is that most of those studies don't consider the global dimensions of the event," Vespig­nani says. "Before you even realize there is an outbreak, it might already be in other places. That changes the game."

One major danger: From London, the smallpox might spread to countries that don't have the health infrastructure of the Western world. In these places it could become potent pandemics that might wash over into still more nations. And that's not only possible for attacks in cities near the less-developed corners of the world. No matter what metropolis a bioterrorist targets for harm, the dispersion of disease unfolds more or less the same way, at least according to the computer model.

And what might the march of contagions look like? Here are two snapshots showing the ripple effect from a smallpox release in London. These maps show the "probability of each zone of the world of having imported infectious people," says Vespig­nani, both at the time the authorities realize there's an outbreak (top) and two weeks afterward (bottom). Higher probabilities are shown in lighter blue:

Vespig­nani says there are two big things that people should take away from these findings. The first is that governments and international health organizations, whether it be WHO, the CDC or whoever, need to develop contingency plans for a pandemic that originates from afar. "They need to think about sharing resources," he says.

The second is that wanna-be terrorists playing with pathogenic agents ought to consider that a biological attack is a double-edged sword. "They think they're going to affect only the area that they target. But quickly and easily, it will spread all over the world," perhaps even right back to their own motherland. "Using these kinds of weapons, there is no winner, for sure."

Top image: anyaivanova / Shutterstock.com

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