In 1900, the infamous Galveston hurricane struck out of the blue, catching the population unaware and killing between 6,000 and 12,000 people, still the largest natural disaster in US history. A hundred and 12 years later, forecasters at the National Hurricane Center tracked and predicted--with astonishing accuracy--the route that hurricane Sandy took en route to slamming into the Jersey Shore. Now, in a pioneering study just published in the Proceedings of the National Academy of Science, researchers at Columbia University and the National Center for Atmospheric Research have reported successfully adapting the same techniques used by meteorologists to predict an even more lethal force of nature: influenza epidemics.
Worldwide, the flu sickens 10 million people each year, killing between one-quarter to one-half million victims. Just as reliable weather forecasting saves lives by giving a heads-up to those in harm's way, so do the researchers hope that accurate, localized flu forecasts will help minimize the toll taken by future epidemics. (Feel a sneeze coming on? Try these 10 Ways to Stop a Cold in Its Tracks.)
"Public health and government agencies clearly would benefit from having objective forecasts that provide them with a larger lead time for preparedness," says Jeffrey Shaman, Ph.D., an assistant professor at Columbia. "It would give them a leg up on vaccinations, antivirals, and possibly even school closures. On the individual level, a flu forecast could help motivate people to take the steps they need to avoid the flu, such as getting vaccinated 2 weeks or more in advance."
Start with a model
Complex systems like the weather and flu transmission change through time in ways scientists call "nonlinear" or even "chaotic." In order to predict the course they're likely to take, researchers begin by constructing a mathematical model that attempts to factor in known influences on the system's behavior. Westerly winds over the Atlantic Ocean, for example, tend to cause hurricanes to hook right and head to the North. Similarly, reductions in absolute humidity each winter enhance flu transmissibility, in part, by allowing virus particles to survive longer.
But even the best mathematical models can't hope to account for the myriad complexities of the real world. "It's like the butterfly effect, the whole chaos thing," explains Shaman. "Little tiny perturbations will cause an imperfect model to fly off and predict that something will happen when, in fact, something radically different actually happens." (Another cure for the common cold? Eat! Here are 5 Fruits that Fight the Flu.)
