The Hawai'i Department of Health has confirmed the state's fourth death associated with swine flu, a man in his 50s who died on July 19 at a Big Island hospital.

Like the previous three deaths in Hawai'i, the Big island patient had other health conditions, the department said yesterday.

"The primary cause of death was influenza pneumonia, but the patient's underlying medical conditions were a contributing factor," said Dr. Sarah Park, chief of the Disease Outbreak Control Division and state epidemiologist.

"The department currently is focusing its investigation and testing on critical cases and focused clusters as a way to monitor when this pandemic virus might change to something that causes more severe disease."

No other information about the patient's medical condition before death was released.

The national Centers for Disease Control and Prevention's weekly update of confirmed cases of swine flu show 1,424 cases in Hawai'i.

Previous deaths in Hawai'i linked to novel H1N1 influenza were to a man in his late 40s who died July 10 at The Queen's Medical Center; a woman in her early 50s who died July 7 at Kona Community Hospital; and a woman in her 60s who died June 19 at Tripler Army Medical Center.

The CDC said yesterday that up to 40 percent of Americans could get swine flu this year and next and several hundred thousand could die without a successful vaccine campaign and other measures.

The CDC's estimates are roughly twice the number of those who catch flu in a normal season.

First identified in April, swine flu has likely infected more than 1 million Americans, the CDC believes, with many of those suffering mild cases never reported. There have been 302 deaths and 43,771 laboratory-identified cases of H1N1, according to numbers released yesterday.

Health officials say flu cases may explode in the fall, when schools open and become germ factories, and the new estimates dramatize the need to have vaccines and other measures in place.

A world health official said the first vaccines are expected in September and October. The United States expects to begin testing on some volunteers in August, with 160 million doses ready in October.

The estimates are based on a flu pandemic from 1957, which killed nearly 70,000 in the United States but was not as severe as the infamous Spanish flu pandemic of 1918-19. The number of deaths and illnesses from the new swine flu virus would drop if the pandemic peters out or if efforts to slow its spread are successful, said CDC spokesman Tom Skinner.

"Hopefully, mitigation efforts will have a big impact on future cases," he said.

Besides pushing flu shots, health officials might urge measures such as avoiding crowded places, handwashing, cough covering and timely use of medicines such as Tamiflu.

DEATH ESTIMATES

Because so many more people are expected to catch the new flu, the number of deaths over two years could range from 90,000 to several hundred thousand, the CDC calculated. Again, that is if a new vaccine and other efforts fail.

In a normal flu season, about 36,000 people die from flu and its complications, according to the American Medical Association. That, too, is an estimate, because death certificates don't typically list flu as a cause of death. Instead, they attribute a fatality to pneumonia or other complications.

The World Health Organization says as many as 2 billion people could become infected in the next two years — nearly a third of the world population.

The agency's committee on vaccines will meet Wednesday to issue recommendations for the new swine flu vaccine.