Federal health officials said Thursday that almost 10,000 people have died of the swine flu since April, a significant jump from mortality numbers released last month. A month ago, the Centers for Disease Control and Prevention estimated that only about 4,000 had died. Officials also said that 50 million Americans, one sixth of the country, have caught the disease, and that 213,000 people have been sick enough to be hospitalized. Several flu experts said they were not shocked by the sudden jump because the new figures were as of Nov. 14, when this fall's wave of swine flu cases was reaching its peak.