WASHINGTON H1N1 swine flu killed an estimated 3,900 Americans from April to October, including more than 500 children, U.S. health officials said on Thursday.
Better data than was previously available shows the flu pandemic has infected an estimated 22 million Americans and put 98,000 in the hospital, the U.S. Centers for Disease Control and Prevention said.
Children account for 8 million of the infected, 36,000 of those hospitalized and 540 deaths.
"We think the 540 number is a better estimate for the big picture that we are getting out there," the CDC's Dr. Anne Schuchat told reporters.
About 82 U.S. children die in an average flu season. The CDC said H1N1 has produced the worst flu season in the United States since 1997, when current measurements started.
"What we are seeing in 2009 is unprecedented," Schuchat said," Schuchat said.
The CDC said doctors need to treat severe cases quickly with antiviral drugs such as Tamiflu, made by Roche AG, Relenza, made by GlaxoSmithKline or for especially grave hospitalized cases, peramivir, made by BioCryst.
Schuchat stressed the pandemic was not worsening but noted that it takes time to gather data on flu cases and deaths. The count released on Thursday is not an actual reckoning of deaths but an extrapolation based on detailed data from 10 states.
CDC's previous estimate of U.S. flu deaths was 1,200.
In an average flu season, about 36,000 Americans die and 200,000 are hospitalized with 90 percent of deaths and hospitalizations among people over 65.
With H1N1, 90 percent of those infected and seriously ill are younger adults and children.
Schuchat said the pandemic would likely continue through the winter and early spring. "We have a long flu season ahead of us," she said.
Most confirmed flu cases are H1N1 and about 30 percent of people who show up at the doctor's office and are actually tested for influenza turn out to have flu, as opposed to some other infection.
(Additional reporting by Julie Steenhuysen in Chicago, edited by Alan Elsner)