Computer models suggest strategies for stopping disease outbreaks
SEATTLE, WA – New modeling studies show how bioterror agents may spread throughout the population in the case of an attack and how such attacks can be detected. Scientists reported these findings, which should help policymakers design effective public health measures, today at the 2004 AAAS (Triple-A-S) Annual Meeting.
If a bioterror attack should occur, early detection would be crucial for saving lives. But how could local public health officials know whether one patient's symptoms were part of a larger trend?
"Historically, disease surveillance has worked by identifying and diagnosing individuals with conditions of interest and reporting them to public health departments, but diagnosis takes a long time….Since September 11, especially, people have been looking for ways to get an early idea of when outbreaks are occurring," said Michael Stoto of the RAND Corporation, a speaker at the annual meeting of the American Association for the Advancement of Science (AAAS).
A controversial solution would be to implement a large-scale surveillance system based on information from health care providers.
Surveillance would be effective and economical according to Ken Kleinman of Harvard Medical School. In an article published in the biweekly American Journal of Epidemiology, Kleinman and his colleagues describe a statistical model used in an experimental system, funded by the U.S. Centers for Disease Control, which collects data from several large physician practices, HMOs and a national nurse call center.
"Our results indicate that there is great value to using surveillance and statistical modeling to detect early signs of outbreaks such as anthrax," Kleinman said. "The data are routinely collected during the course of business and need only statistical analysis to provide advance warning of an attack."
The system protects patients' privacy by identifying them only in terms of the number of people sick in each zip code, according to Kleinman.
In contrast, a study by Stoto and colleagues suggests surveillance may not be worth the trouble. Reporting their findings in an article in the February issue of the quarterly magazine, Chance, Stoto's team analyzed four different statistical detection algorithms using daily counts of patients with influenza-like illness from a hospital emergency department.
"There's a relatively narrow window when [surveillance] would make a difference," Stoto said. "If an outbreak were so large that lots of people got sick at the same time, you wouldn't need surveillance. And if the outbreak were small, these techniques wouldn't detect it."
Even after a possible outbreak was detected, he added, more time would be needed to characterize the agent, identify people who might have been exposed and determine a public health response.
Given these limitations, plus the logistical and economic hurdles, city and state health departments should be "cautious" in investing in surveillance systems, according to Stoto.
If a smallpox outbreak were to occur, how many people in contact with a patient should be vaccinated? How long should people take antibiotics if they've been exposed to anthrax? One of the unsettling aspects of a possible bioterror attack is that researchers can't answer these questions by studying how the pathogens travel among real human beings. Instead, they have turned to sophisticated computer models to simulate the phenomenon.
For smallpox, a new study by Ira Longini of Emory University and colleagues suggests that the current U.S. government control policy – isolating new cases and vaccinating their close contacts – should be sufficient to contain a relatively wide-scale release of the virus.
Longini's team will report their results, from a simulation of the possible paths of a smallpox epidemic that initially infects 500 people, in a study submitted to a peer-reviewed journal.
If anthrax were intentionally unleashed, the length of time that antibiotics treatment should last would depend on how many spores a patient had inhaled, according to Ron Brookmeyer of Johns Hopkins University. While the U.S. Centers for Disease Control recommended a 60-day antibiotics regimen for people exposed to this pathogen after the 2001 outbreak, someone who inhaled a higher dose may need a regimen lasting as long as four months, Brookmeyer and his colleagues have found.
Brookmeyer's team also has evaluated the time it takes to distribute antibiotics to the public and what happens if people do not adhere to the recommended antibiotic policy. One of the most important factors in preventing disease is getting antibiotics quickly to persons who were exposed, he said.
In 2001, many people did not receive antibiotics until more than nine days after exposure to anthrax spores, and many did not take the antibiotics for the full 60 days, according to Brookmeyer.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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