WASHINGTON - The Bush administration is scrambling to prepare the nation for a possible global rampage by a new flu germ that it fears could kill nearly 2 million Americans, sicken tens of millions more and shatter the economy. The key question is how much preparation can be done before a calamity strikes that, in a worst-case scenario, could make the health system collapse; overwhelm morgues; close schools, airports and harbors; end public gatherings; require strict quarantines; and cripple businesses and vital public services by mass absenteeism. "You're looking at a nation-busting event," warned Tara O'Toole, director of the Center...