What you need to know about the new swine flu

WASHINGTON " As the new swine flu spreads, people have lots of questions about how it affects their day-to-day life. Here are some answers.

Q: How easy is it to catch this virus?

A: It's spreading as easily as regular winter flu, which infects millions each year. Early estimates are that 25 percent to 30 percent of family members are getting sick once a relative brings it home.

Q: How dangerous is it?

A: Nobody knows yet. Genetically, it doesn't share the same traits that made the infamous 1918 pandemic so deadly, nor does it seem as virulent as the bird flu that scientists have tracked for several years. While Mexico reported many deaths, the virus is causing less severe illness in the U.S. In fact, the Centers for Disease Control and Prevention says most cases so far haven't needed medical attention.

Q: Could I have some immunity?

A: Since it's a never-before-seen mix of mostly pig but also human and bird viruses, the CDC has cautioned that's unlikely. But it is a member of the H1N1 family of flu viruses, which circulate widely. Flu specialist John Treanor at the University of Rochester says people born before 1957 spent their childhood repeatedly exposed to H1 viruses. So experts are withholding final judgment on that question.

Q: Is it treatable?

A: Yes, with the standard anti-flu drugs Tamiflu and Relenza. They lessen symptoms if taken within 48 hours of the first symptoms.

Q: How long do I have to worry if I just got back from Mexico?

A: The incubation period is two days to seven days, regardless of where you were exposed.

Q: How long should I stay home if I get the flu?

A: Certainly call your doctor about bad symptoms or if you're at all worried, especially if you have any chronic condition, such as asthma, that makes you more susceptible to any kind of flu. But other than going out for medical care, stay home for seven days or for one day after symptoms end. The CDC also says family members should consider staying home or decreasing their contact with others in case they're incubating the infections.

Q: Why are so many schools closing?

A: It's not clear just how much good school closings do in slowing flu's spread. It doesn't help much if kids then gather at the mall or a friend's house or day care. But because children spread all kinds of viruses easily " they don't wash as well, have close contact in crowded classes, and sometimes are contagious for a few days longer than adults " the CDC has advised schools with cases to consider closing for at least 14 days.

Q: Is it safe to fly? How about the subway?

A: Yes, the CDC says. Just don't travel if you're sick " stay home.

Q: Do I need a mask in crowded areas?

A: The CDC hasn't yet recommended that anyone other than health workers use masks.

Q: Why hasn't the U.S. closed the border with Mexico?

A: By the time authorities detected the new virus, it already had spread here. That makes closing the border moot, the Obama administration says.

For more information cdc.gov/swineflu or call CDC's 24-hour hot line, in English or Spanish, at 1-800-CDC-INFO.