Here's what you need to know:
Q: How do I protect myself and my family?
A: For now, take commonsense precautions. Cover your coughs and sneezes, with a tissue that you throw away or by sneezing into your elbow rather than your hand. Wash hands frequently; if soap and water aren't available, hand gels can substitute. Stay home if you're sick and keep children home from school if they are.
Q: How easy is it to catch this virus?
A: Scientists don't yet know if it takes fairly close or prolonged contact with someone who's sick, or if it's more easily spread. But in general, flu viruses spread through uncovered coughs and sneezes or — and this is important — by touching your mouth or nose with unwashed hands. Flu viruses can live on surfaces for several hours, like a doorknob just touched by someone who sneezed into his hand.
Q: In Mexico, officials are handing out face masks. Do I need one?
A: The CDC says there's not good evidence that masks really help outside of health care settings. It's safer just to avoid close contact with someone who's sick and avoid crowded gatherings in places where swine flu is known to be spreading. But if you can't do that, CDC guidelines say it's OK to consider a mask — just don't let it substitute for good precautions.
Q: Is swine flu treatable?
A: Yes, with the flu drugs Tamiflu or Relenza, but not with two older flu medications.
Q: Is there enough?
A: Yes. The federal government has stockpiled enough of the drugs to treat 50 million people, and many states have additional stocks. As a precaution, the CDC has shipped a quarter of that supply to the states to keep on hand just in case the virus starts spreading more than it has so far.
Q: Should I take Tamiflu as a precaution if I'm not sick yet?
A: No. "What are you going to do with it, use it when you get a sniffle?" asks Dr. Marc Siegel of New York University Langone Medical Center and author of "Bird Flu: Everything you Need To Know About The Next Pandemic." Overusing antiviral drugs can help germs become resistant to them.
Q: How big is my risk?
A: For most people, very low. Outside of Mexico, so far clusters of illnesses seem related to Mexican travel. New York City's cluster, for instance, consists of students and family members at one school where some students came back ill from spring break in Mexico.
Q: Why are people dying in Mexico and not here?
A: That's a mystery. First, understand that no one really knows just how many people in Mexico are dying of this flu strain, or how many have it. Only a fraction of the suspected deaths have been tested and confirmed as swine flu, and some initially suspected cases were caused by something else.
Q: Should I cancel my planned trip to Mexico?
A: The U.S. did issue a travel advisory Monday discouraging nonessential travel there.
Q: What else is the U.S., or anyone else, doing to try to stop this virus?
A: The U.S. is beginning limited screening of travelers from Mexico, so that the obviously sick can be sent for treatment. Other governments have issued their own travel warnings and restrictions. Mexico is taking the biggest steps, closings that limit most crowded gatherings. In the U.S., communities with clusters of illness also may limit contact — New York closed the affected school for a few days, for example — so stay tuned to hear if your area eventually is affected.
Q: What are the symptoms?
A: They're similar to regular human flu — a fever, cough, sore throat, body aches, headache, chills and fatigue. Some people also have diarrhea and vomiting.
Q: How do I know if I should see a doctor? Maybe my symptoms are from something else — like pollen?
A: Health authorities say if you live in places where swine flu cases have been confirmed, or you recently traveled to Mexico, and you have flulike symptoms, ask your doctor if you need treatment or to be tested. Allergies won't cause a fever. And run-of-the-mill stomach bugs won't be accompanied by respiratory symptoms, notes Dr. Wayne Reynolds of Newport News, Va., spokesman for the American Academy of Family Physicians.
Q: Is there a vaccine to prevent this new infection?
A: No. And CDC's initial testing suggests that last winter's flu shot didn't offer any cross-protection.
Q: How long would it take to produce a vaccine?
A: A few months. The CDC has created what's called "seed stock" of the new virus that manufacturers would need to start production. But the government hasn't yet decided if the outbreak is bad enough to order that.
Q: What is swine flu?
A: Pigs spread their own strains of influenza and every so often people catch one, usually after contact with the animals. This new strain is a mix of pig viruses with some human and bird viruses. Unlike more typical swine flu, it is spreading person-to-person. A 1976 outbreak of another unusual swine flu at Fort Dix, N.J., prompted a problematic mass vaccination campaign, but that time the flu fizzled out.
Q: So is it safe to eat pork?
A: Yes. Swine influenza viruses don't spread through food.
Q: And whatever happened to bird flu? Wasn't that supposed to be the next pandemic?
A: Specialists have long warned that the issue is a never-before-seen strain that people have little if any natural immunity to, regardless of whether it seems to originate from a bird or a pig. Bird flu hasn't gone away; scientists are tracking it, too.