Swine flu could infect as much as half of the US population this fall and winter and cause up to 90,000 deaths, President Barack Obama's science advisors warned Monday.
Laying out a "plausible scenario" for the epidemic's impact in the United States, the report painted a grim picture of stress on the US health care system as it struggles to cope with a flood of flu patients.
The epidemic's resurgence could "produce infection of 30-50 percent of the US population this fall and winter, with symptoms in approximately 20-40 percent of the population (60-120 million people), more than half of whom would seek medical attention," the report said.
As many as 1.8 million people could be admitted to hospitals with up to 300,000 of them requiring treatment in intensive care units.
"Importantly, these very ill patients could occupy 50-100 percent of all ICU beds in affected regions of the country at the peak of the epidemic and could place enormous stress on ICU units, which normally operate close to capacity," it said.
The epidemic, it said, "could cause between 30,000 and 90,000 deaths in the United States, concentrated among children and young adults," it said.
That compares with 30,000 to 40,000 deaths from seasonal flu each year, mainly among people over age 65.
The report said the epidemic poses "especially high risks" for people with pre-existing conditions such as pregnant women and patients with neurological disorders, respiratory impairment, diabetes or severe obesity.
It also mentioned Native Americans as being at risk from the swine flu.
The flu's resurgence could occur as early as September when the school term begins, and peak in mid-October.
But a vaccine against the A(H1N1) virus is only projected to be available in mid-October, and it will take vaccinated individuals several more weeks to develop protective immunity, the report said.
"This potential mismatch in timing could significantly diminish the usefulness of vaccination for mitigating the epidemic and could place many at risk of serious infection," it said.
The report by the President's Council of Advisors on Science and Technology (PCAST) said that while the virus is "unlikely to resemble the deadly flu pandemic of 1918-19," the current strain still "poses a serious health threat."
According to the latest official US figures, the 2009 swine flu strain has already killed 522 people in the United States and hospitalized almost 8,000 people since it emerged in Mexico at the end of April.
The group recommended accelerating preparation of flu vaccines for distribution to high-risk individuals and clarifying guidelines for the use of antiviral medicines.
Advisors also called on the public to stay informed on A(H1N1)'s expected spread as the northern hemisphere's regular flu returns with the colder months.
These efforts involve using social networking sites on the Internet to propagate health messages and an "intensive public education" campaign to promote awareness to the threat.
The White House also needs to create a post that has "primary authority to coordinate key decisions" for fighting the pandemic, the report said.
Among other recommendations are for workplaces to "liberalize rules for absenteeism" so employees are not pressured to come to work when they feel sick.
Overall, the PCAST gave the administration positive reviews for its preparation.
"The Federal Government's response has been truly impressive and we've all been pleased to see the high level of cooperation among the many departments and agencies that are gearing up for the expected fall resurgence of H1N1 flu," said PCAST co-chair Harold Varmus.
"This virus has pulled us all together in common cause," said another PCAST co-chair, Eric Lander. "The preparations are the best ever for an influenza pandemic," he said.
Over 20 pharmaceutical companies around the world are racing to test, produce and distribute more than a billion doses of the vaccines in anticipation of the second wave of infection.
A(H1N1) has created a health crisis in Latin America throughout the southern continent's winter months, causing more than 1,300 deaths, according to an AFP tally of individual government tolls.