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[INTERACTIVE: Interactive guides to spread of swine flu]
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[TRAVEL ALERT: What the CDC wants you to know ]
The Maricopa County Health Department reported that the woman in her late 40s died last week of what appears to be complications of the new strain of influenza.
Laboratory tests confirmed that the woman was infected with the flu strain. The federal Centers for Disease Control and Prevention is expected to add her to the official national tally on Friday, health department spokeswoman Jeanene Fowler said.
"Unfortunately, we knew this was coming. Flu is serious, especially for those with underlying health conditions," said Bob England, director of the health department.
England declined to say where the woman was from or release further details.
"While this marks the first death in our state related to swine flu, the case counts are expected to continue rising for some time to come," said Will Humble, acting director of the Arizona Department of Health Services.
Arizona's case would bring the number of swine flu-related deaths in the nation to four and put the worldwide death toll at 70.
The other deaths in America were in Texas -- a Mexican toddler and a school teacher who died days after giving birth -- and a man in his 30s in Washington state. Each suffered from other illnesses when they were infected with the virus.
Arizona had 261 confirmed cases of swine flu in nine of the state's 15 counties as of Thursday. The state's first case was identified on April 29.
Officials closed more than a dozen schools in the state before they learned swine flu wasn't as serious as first feared. All schools have reopened.
Health officials urge members of the public to cover their coughs if they're sick and wash their hands throughout the day to avoid spreading viruses.
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