"Anthrax spores are expelled from the lungs at a specific rate. Our model calculates the time it takes the body to expel these spores. A single spore left behind can germinate to cause disease," explained Ron Brookmeyer, PhD, lead author of the study and professor of biostatistics at the School of Public Health. "The model we developed shows that larger exposures to anthrax spores take longer to expel and require longer antibiotic therapy. Sixty days of antibiotics provides adequate protection in outbreaks with low exposure to spores. However, four months of antibiotics are required for outbreaks in which persons are exposed to large numbers of spores."
Dr. Brookmeyer and his colleagues tested their model using data from the 2001 anthrax attack on the United States and the 1979 anthrax outbreak near a biological weapons plant in Sverdlovsk, Russia. In both cases, the model's predictions were consistent with the actual illness rates.
"During the 2001 U.S. anthrax attacks, many people failed to take the recommended 60-day course of antibiotics. Full compliance was about 60 percent or less in some cases. Our model showed that the reason they didn't get sick even without the antibiotics was because the anthrax spore exposure levels were very low. If the exposure levels were higher, there would have been more casualties," said Dr. Brookmeyer.
"Modeling the Optimum Duration of Antibiotic Prophylaxis in an Anthrax Outbreak," was written by Ron Brookmeyer, Elizabeth Johnson and Robert Bollinger.
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Proceedings of the National Academy of Sciences