WASHINGTON – The Earth may be on the brink of a worldwide epidemic from a bird flu virus that may mutate to become as deadly and infectious as viruses that killed millions during three influenza pandemics of the 20th century, a federal health official said Monday.

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"The science here is all alerting us that we have a great deal to be concerned about," she said.

The CDC chief said her agency is getting ready for a possible pandemic next year.

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