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LANL Analysis Shows How To Slow Spread

By Olivier Uyttebrouck
Journal Staff Writer
       Los Alamos National Laboratory scientists using some of the most sophisticated computers in the world helped develop a plan to slow the spread of a nasty flu strain to give health officials time to produce and distribute an effective vaccine.
    Some of their conclusions: stay home, wash your hands, take your medicine and consider closing schools. Don't bother trying to limit domestic travel.
    Some strategies work better than others in slowing the spread of the virus, a LANL researcher said Tuesday.
    Factors such as school closings and weather are important in the spread of influenza, said Timothy Germann, a research scientist at LANL and a lead author of a study that modeled the spread of pandemic influenza.
    "Flu doesn't spread as fast over the summer months, partly because schools are closed," Germann said. Warm, humid weather appears to slow transmission of the influenza virus, he said.
    Germann and other researchers devised computer models that simulated the U.S. population, complete with school, workplace and household groups and commuting and travel patterns.
    The model simulated the spread of a virulent flu strain similar to that of the 1918 flu pandemic that killed millions of people worldwide.
    "Then we tried all these different interventions to see which ones were most effective," he said. "Interventions" included factors such as antiviral drugs like Tamiflu, and "social distancing" techniques such as closing schools and workplaces, limiting travel, and hygienic techniques such as hand-washing.
    "No single strategy by itself was very effective, Germann said. "They all have weaknesses.
    "But the hygiene, the social distancing and Tamiflu can slow down the spread significantly. They can buy time for vaccines to be produced and distributed."
    The study, published in April 2006 issues of the Proceedings of the National Academy of Sciences, was funded by the Department of Homeland Security and the federal Health and Human Services Department. The agencies sought the study after early cases of bird flu in 2003 prompted fears of a pandemic.
    One key tool for slowing the spread of a pandemic involves closing schools, Germann said.
    "Closing schools is a very effective way to slow transmission just because so much of it in the early stages occurs among children," Germann said. Giving children the first available doses of flu vaccine also helps slow the spread, he said.
    Travel restrictions did little to slow the spread of a pandemic, according to the study.
    The simulations found "that the rapid imposition of a 90 percent reduction in domestic travel would slow the virus spread by only a few days to weeks" without changing the eventual size of the outbreak, the authors wrote.
    German said the 1918 flu appears to have been be more virulent than the current swine flu strain that initially appeared in Mexico.
    The simulation also found that about one-third of the people infected could pass the virus on to others but show no symptoms themselves.





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