Scientists dig for lessons from past pandemics

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(CNN) -- If there's a blessing in the current swine flu epidemic, it's how benign the illness seems to be outside the central disease cluster in Mexico. But history offers a dark warning to anyone ready to write off the 2009 H1N1 virus. ....It looks superficially like an academic feud, but in this field, different conclusions can suggest radically different approaches to quashing a pandemic. Nowhere is this more true than in research that builds computer models to predict the spread of outbreaks, based on previous ones. Markel, along with most analysts, says that in prior pandemics, the so-called R-naught number -- the number of new infections caused by each infected person -- has been approximately 2.0. The current U.S. pandemic control strategy is based on computer simulations that assume a flu virus with an R-naught between 1.6 and 2.4. Last year, however, Simonsen and Viggo Andreasen concluded that the true R-naught of the 1918 flu virus was probably somewhere between 3 and 4. Since an epidemic grows exponentially -- each person sickens three others, each of whom infects three more, and so on -- this is a tremendous difference. "It says it's going to be harder than we thought" to control a pandemic, Simonsen says. Barry agrees. "I do think that some of these things, like isolating [sick people], will take off some of the edge. We hope they'll do more than that. But to think they'll stop a pandemic, that is just not going to happen."