A woman in Arizona suffering from a lung condition has apparently become the fourth person in the nation to die with swine flu, authorities said Thursday.

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.

Bob England, director of the health department, said Arizonans should not panic because of the death.

"You should have the same level of concern about this as you do about regular seasonal flu," he said. "Hundreds of our neighbors die each year right in Maricopa County from regular seasonal flu."

England declined to say where the woman was from or release further details.

Arizona's case would bring the number of swine flu deaths in the nation to four and put the worldwide death toll at 70

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.