Boston and Seattle football fans beware! Cities with teams in the Super Bowl see a big spike in flu deaths, according to a new Tulane University study. Using county-level statistics from 1974-2009, researchers found that having a team in the big game caused an 18% increase in flu deaths among those over 65 years old, historically the most vulnerable to influenza.

The reason? The playoffs and championship games bring more people together at the height of flu season to cheer on their teams — and spread germs — in close quarters. The virus can travel six feet in the air after a sneeze, says lead author Charles Stoecker.