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 put together an 86-page report to the White House assessing the government's response to the
first influenza pandemic in 41 years.
Although most of the cases probably would be mild, up to 300,000 people could require intensive care.
"This is going to be fairly serious," said Harold E. Varmus of Memorial Sloan-Kettering Cancer Center in New York, "It's going to stress every aspect of our health system."
While the seasonal flu is associated with 30,000 to 40,000 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, sick -- and possibly to 30,000 to 90,000 deaths.
And while most deaths during a typical flu season occur in the elderly, swine flu is more likely to kill children and young adults.
The outbreak could turn out to be milder, too. The primary purpose of the estimates id to help guide planning for the public.
For example, it was estimated that the outbreak could peak in mid-October.
"This isn't the flu that we're used to," said Health and Human Services Secretary Kathleen Sebelius.
The pandemic has caused significant disruptions and economic damage and has contributed to the deaths of more than
If you have children going to school and they show any signs of being sick...keep them home. Also make sure you ask your child to watch and see if any other students have flu like symptoms.
Swine flu, or 2009 H1N1, is a virus that is a chimera -- a mix of a number of human, swine and avian influenza virus genes. Most important, it contains a surface protein, H1, that has not been seen in the human population before, so very few people have any immunity from infection with this virus.
The symptoms are very similar to those of seasonal flu: high fever, cough, aches and pains, sneezing and feeling very tired. In some people, such as pregnant women, the disease can progress to a serious form involving shortness of breath and other severe complications.
Who appears to be most at risk for catching it?
Has H1N1 mutated and become more or less severe since the spring?
The virus has not changed to become more infectious or cause more severe disease since it emerged in humans in April.
If I had swine flu last spring, do I need to be vaccinated this fall?
If you had a confirmed case of 2009 H1N1, then you most likely have immunity to the virus and would be protected from infection. However, you should still get the vaccine, particularly if you are in one of the high-risk groups, so you can get an even stronger immune response.
What should I do if I think I have H1N1?
Always consult a physician for specific medical advice, but for most people, if you start to feel flulike symptoms (fever, dry cough), simply go home or stay there, rest and take plenty of fluids. There are no specific medical treatments recommended. If the disease progresses to a more severe form (you experience trouble breathing, shortness of breath, chest pains, dizziness or vomiting), immediately contact your physician so you can begin treatment with antivirals and get other medical care.
How do I take care of someone I'm living with who has H1N1?
The Centers for Disease Control and Prevention has guidelines for what to do if you find yourself caring for someone with the flu: Basically, you should minimize your exposure to the person, make sure you remind the sick person to practice good etiquette for coughing and sneezing (cough or sneeze into a disposable tissue that you get rid of immediately, or into your sleeve) and have everyone in the household wash their hands regularly.
I've seen antibacterial, alcohol-based and other soaps. What should I use?
Any kind of soap will work against influenza viruses, as long as you are sure to wash your hands well. Don't just get them wet with water and walk away. Alcohol-based hand sanitizers work well against influenza if your job doesn't allow you to wash your hands regularly.