Some 22 million Americans have been infected with the H1N1 virus, which has caused over 4,000 deaths since its spread began, according to revised figures by the Centers for Disease Control.

"The changes reflect new surveillance methods thought to be more accurate but also show that figuring out the death toll from influenza is not a precise science," ABC News noted.

The death toll noted by the CDC is triple that reported on Wednesday.

Officials urged that the numbers are not a sign of swine flu spreading further or becoming more lethal, but the government's methodology for estimating its spread becoming more accurate.

"I don't really think the public should be more worried, as the revised estimate does not reflect a change in the virulence of, or severity of, infection due to the virus," ABC News quoted Wake Forest University School of Medicine Dr. Christopher Ohl as saying.

The threat of swine flu has been largely overestimated in the media. H1N1 is not much more deadly than standard seasonal flu, which kills over 36,000 Americans every year.

This video was published to YouTube by the Associated Press on Monday, November 16, 2009.

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