CNN answers your FAQs on swine flu

CNN wants to help its viewers and online users get answers surrounding the outbreak of swine flu in Mexico. We've had an outpouring of questions come in. The following are among the most frequently asked questions.

Q: Why is it more deadly in Mexico than anywhere else it’s surfaced?

CNN: The short answer is investigators don’t know. The deaths have occurred in healthy people, as opposed to those usually most at risk from the flu: the young, the old and those with compromised immune systems. The same thing happened in recent years with the SARS and avian flu outbreaks. The spreading virus starts a cascade within the body as the immune system overreacts. Fluid builds up in the lungs and inflammatory cells throughout the body react to the infection.

Q: Does the normal influenza vaccine offer protection against swine flu virus?

CNN: It may offer some. This particular virus seems to be a combination of several different strains: two strains of swine flu, one strain of bird flu and one strain of human flu. It's the human flu portion of the virus that that the flu vaccine may offer some protection against.

Q: Can animals, such as dogs or cats, contract the swine flu? If so, can they transfer it to humans?

CNN: There is no evidence that dogs and cats can contract swine flu. Still, this is a new strain of swine flu virus, and investigators can’t rule it out until more tests are done. In the past, the avian H5N1 flu has infected domestic cats and at least one dog in Thailand, according to the scientific literature. In 2004, the equine H3 virus appeared to infect dogs. There have been no reports of dogs or cats spreading the flu to people.

Q: How long will it take if a person has the flu before they show symptoms?

CNN: The typical incubation period for influenza is 1-4 days, according to the Centers for Disease Control and Prevention. The symptoms are similar to the common flu. They include fever, lethargy, lack of appetite, coughing, runny nose, sore throat, nausea, vomiting and diarrhea.

Q: How does a person contract swine flu? Does it come from pigs?

CNN: Swine flu may have come from pigs originally, but it is now being spread from among people. The virus spreads the same way the seasonal flu does. When an infected person coughs or sneezes around another person, the latter is put at risk. People can become infected by touching something with the flu virus on it and then touching their mouth, nose or eyes. An infected person can pass the virus to another before any symptoms even develop

Q: Should I avoid traveling to Mexico because of the swine flu?

CNN: The U.S. Centers for Disease Control and Prevention has recommended that Americans avoid all "non-essential" travel to Mexico.

Q: The swine flu has been labeled as  H1N1. The strain that killed millions of people in 1918 was also labeled H1N1; is it the same virus?

CNN: It is not the same virus. The current strain is a new variation of an H1N1 virus, which is a mix of human and animal versions. H1 refers to type of hemagglutinin, which is involved in the virus gaining entry into a target cell. N1 refers to neuraminidase, an enzyme that allows the release of copies of the virus from infected cells. A new variation can be created when an animal is infected with two or more different viruses at the same time. The viruses can exchange genes. This can be particularly dangerous because people may not have any immune defense against it.

You may have heard to this swine flu virus refered to as "Type A." There are three general types of influenza, Type A, Type B and Type C. Type A occurs in many species and historically has been the sole cause of pandemics.

Q: Where did this swine flu come from?  How did the outbreak occur in Mexico?

CNN: Researchers do not know yet know. People usually get swine flu from infected pigs. For example, farmers handling infected pigs can contract the virus. However, some human cases have occurred without contact with pigs or places they inhabited.

CNN will continue to answer your questions as the story progresses.