There were 1.8 million to 5.7 million cases of swine flu in the country during the epidemic's first spring wave, according to a new estimate from the Centers for Disease Control and Prevention released Thursday. From 9,000 to 21,000 people were hospitalized as a result, and up to 800 died from April to July, when it largely faded out, according to the estimates, which were conducted by the CDC and the Harvard School of Public Health and published online in the journal Emerging Infectious Diseases. The agency has been working for months on a model that took into account the fact that most flu cases were not tested by doctors and that some people were hospitalized for conditions exacerbated by the flu without the flu ever having been diagnosed.
