About 4,000 U.S. residents, rather than about 1,200, have died of swine flu since the disease emerged in April, according to figures being calculated by epidemiologists for the Centers for Disease Control and Prevention.
The jump does not mean the virus is more dangerous. It's an estimate made by combining laboratory-confirmed deaths from the flu and others that appear to be brought about by flu, although the patient ultimately may have died of bacterial pneumonia, infection or organ failure.
The estimate will not be released until next week because CDC consultants still are looking over the figures, said spokesman Glen Nowak.
It will be a more accurate comparison to the 36,000 deaths from seasonal flu each year, he said. That estimate is based on confirmed cases as well as hospital reports of people who appear to have died after a bout of flu.
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More than 90 percent of seasonal flu victims are older than 65, and many are bedridden, in nursing homes or have serious medical problems such as cancer or heart disease that the flu worsens.
The estimate "does sound much more reasonable," said Ira M. Longini Jr., a flu epidemiologist at the University of Washington. "It doesn't surprise me that it's higher."
Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said the estimate was more accurate "but doesn't change the decisions you'd make from a public health perspective."
"If it was 40,000 deaths rather than 4,000, that would be different," Osterholm said.
Longini said he thought overall deaths likely will be in the 30,000 to 40,000 range;Osterholm said they would "have a long way to go to even get there."