Up to half of the U.S. population could contract swine flu this upcoming flu season, killing up to 90,000 people and hospitalizing 1.8 million, according to a report released by the President's Council of Advisors on Science and Technology. Americans lack immunity to the swine flu, which gives the virus the potential to infect more people than the seasonal flu generally does. And although many people who contract the disease might not show symptoms, and most would not be hospitalized, the pandemic