WASHINGTON - Swine flu could infect half the U.S. population this fall and winter, hospitalizing up to 1.8 million people and causing as many as 90,000 deaths - more than double the number that occur in an average flu season, according to an estimate from a presidential panel.
The virus could cause symptoms in 60 million to 120 million people, more than half of whom might seek medical attention, the President's Council of Advisors on Science and Technology estimated. The numbers were given in an 86-page report to the White House assessing the government's response to the first influenza pandemic in 41 years.
Although most cases probably would be mild, up to 300,000 people could require intensive care, which could tie up ICU beds in some parts of the country at the peak of the outbreak, the council said.
"This is going to be fairly serious," said Harold Varmus of New York's Memorial Sloan-Kettering Cancer Center, who co-chairs the 21-member council. "It's going to stress every aspect of our health system."
The estimates, released Monday, were the first specific numbers by experts on the possible impact of the pandemic in the United States. The "plausible scenario" is based on previous pandemics, especially the 1957-58 Asian flu, and how the swine flu behaved in the United States this spring and during the Southern Hemisphere's winter over the past few months, said Mark Lipsitch of the Harvard School of Public Health. He helped prepare the estimate.
"They are not a prediction, but they are a possibility," he said, noting the estimates are based on assumptions, including that the virus will not mutate into a more dangerous form or infect more older people.
"If it turned out to affect a lot more adults, the severity would be a lot worse," Lipsitch said.
While the seasonal flu causes about 36,000 deaths and 200,000 hospitalizations each year, the lack of immunity to the swine flu virus probably will lead to many more people becoming infected and possibly dying - as many as 90,000, the council said. And while most deaths during a typical flu season are among the elderly, swine flu is more likely to kill children and young adults, the panel said.
The report's primary purpose is to help guide planning to protect the public and improve the government's response to the outbreak. For example, it was estimated the outbreak could peak in mid-October, so the panel urged expediting the availability of a vaccine.
The panel also recommended clarifying how antiviral drugs should be used to fight the pandemic, speeding a decision about whether to approve intravenous antivirals in case they are needed, and improving the system for tracking the spread of the new virus.