- The Washington Times - Monday, August 5, 2002

NEW YORK (AP) Imaginative minds can conjure horribly apocalyptic consequences from a smallpox attack.
After plaguing humanity for centuries and killing 30 percent of those it infected, the disease was eradicated three decades ago so that natural immunity and long-ago vaccinations provide no protection. Unchecked, smallpox could sweep through the U.S. population like a medieval plague.
But with the help of computers, many researchers are concluding that a smallpox attack by terrorists need not produce an uncontrollable public health crisis.
Computer simulations show that the proper combination of post-attack vaccination, quarantine and other public health measures could stop smallpox in its tracks:
A model designed by researchers from the Centers for Disease Control and Prevention found that vaccination and quarantine could stop an outbreak within a year and limit the number of smallpox cases to 4,200 even if 1,000 persons were directly infected by terrorists.
Researchers from Yale University and the Massachusetts Institute of Technology found through another simulation that a massive vaccination program launched as soon as the first smallpox cases were detected could quickly stop the disease from spreading and limit infections to fewer than twice the initial number.
By simulating the daily comings and goings of people in Portland, Ore., researchers from the Los Alamos National Laboratory found that reasonable public health measures combined with people's existing tendency to stay home when they're feeling sick would likely limit the spread of smallpox after an attack.
"I think it's apparent that we can control an outbreak of smallpox if we do the right thing," said Stephen Eubank, a researcher in the Basic and Applied Simulation Science Group at Los Alamos.
"No one can predict the future," said Tara O'Toole, director of the Center for Civilian Biodefense at Johns Hopkins University. "Models can help us imagine it and maybe help us respond."
The Los Alamos model, for example, uses census data to replicate the daily life of every person in Portland, Ore., to see how trips to school, work, malls would spread smallpox through the community.
Mr. Eubank starts the simulation by giving a specific group of people smallpox. It could be a dozen shoppers at a particular mall or a handful of infected terrorists who set about trying to pass their illness to other people. Then he sees how the movements of those initially infected people spread the disease in the population.
Mr. Eubank can also change people's behaviors based on how they feel. For example, he said, "when you contract smallpox you get sick as a dog. It happens about the time you become contagious."
The Los Alamos model simulates that by keeping many of the most contagious people home, not out and about infecting their friends and co-workers. In a smallpox outbreak, if authorities could persuade those who felt sick to stay home perhaps by promising a house call from an infectious disease specialist, Mr. Eubank said many fewer people would be infected.
The surest way to prevent a smallpox attack from killing more than a handful of people would be to vaccinate the majority of the population in advance. But the vaccine itself kills about one person in a million. A universal U.S. vaccination program would likely kill about 300 people and permanently injure thousands more.
Models show, however, that a system in place to vaccinate everyone in a city at the first appearance of smallpox could stop an outbreak in a few weeks, said Edward Kaplan of Yale University.
In the hypothetical case of a smallpox attack that initially infected 1,000 persons, a model designed by Mr. Kaplan and colleagues from MIT calculated that mass vaccination would limit the number of casualties to 1,830 illnesses and 560 deaths in a city of 10 million.
Some people would suffer serious complications from the vaccinations, and about 10 would die. But in the face of a potential smallpox epidemic, Mr. Kaplan believes the odds would almost always favor mass vaccination over a less-aggressive approach.



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