WASHINGTON, April 25 (Xinhua) -- A new swine flu strain has killed as many as 20 people and sickened more than 1,300 across Mexico. Eleven U.S. people were also confirmed to be infected with the virus.

    The World Health Organization announced Saturday that the outbreak in Mexico and the United States constituted a "public health emergency of international concern."

    The following are questions and answers about swine flu:

    What is swine flu?

    Swine flue (Influenza) is a respiratory disease of pigs caused by type A influenza viruses. Outbreaks of swine flu happen regularly in pigs. People do not normally get swine flu, but human infections can and do happen. Most commonly, human cases of swine flu happen in people who are around pigs but it's possible for swine flu viruses to spread from person to person also.

    The new strain found in Mexico and the U.S. is a mixture of swine, human and avian flu viruses.

    Is this new swine flu virus contagious?

    The U.S. Centers for Disease Control and Prevention (CDC) has determined that this virus is contagious and is spreading from human to human. However, at this time, it is not known how easily the virus spreads between people.

    What are the signs and symptoms of swine flu in people?

    The symptoms of swine flu in people are similar to the symptoms of regular human flu, including fever, cough, sore throat, body aches, headache, chills and fatigue. Some people have reported diarrhea and vomiting associated with swine flu. In the past, severe illness (pneumonia and respiratory failure) and deaths have been reported in swine flu patients. Like seasonal flu, swine flu may cause a worsening of underlying chronic medical conditions.

    How serious is swine flu infection?

    Like seasonal flu, swine flu in humans can vary in severity from mild to severe. From 2005 until January 2009, 12 human cases of swine flu were detected in the U.S. with no deaths occurring. However, swine flu infection can be serious. In September 1988, a previously healthy 32-year-old pregnant woman in Wisconsin was hospitalized for pneumonia after being infected with swine flu and died 8 days later.

    How do people catch swine flu?

    Spread of swine flu can occur in two ways: through contact with infected pigs or environments contaminated with swine flu viruses; through contact with a person with swine flu. Human-to-human spread of swine flu has been documented also and is thought to occur in the same way as seasonal flu. Influenza is thought to spread mainly person-to-person through coughing or sneezing of infected people.

    Are there medicines to treat swine flu?

    Health authorities in some countries recommend the use of oseltamivir (Tamiflu) or zanamivir (Relenza) for the treatment and/or prevention of infection with these swine influenza viruses. These antiviral drugs can keep flu viruses from reproducing in one's body and may also prevent serious flu complications.

    How long can an infected person spread swine flu to others?

    People with swine influenza virus infection should be considered potentially contagious as long as they are symptomatic and possible for up to seven days following illness onset. Children, especially younger children, might potentially be contagious for longer periods.

    Are there any precautionary measures against swine flu?

    There is no vaccine available right now to protect against swine flu. There are everyday actions that can help prevent the spread of germs causing respiratory illnesses like influenza, such as hand-washing with alcohol-based hand cleaners especially after coughing or sneezing and avoiding close contact with sick people.

    If one gets sick with influenza, the patient is better to stay home from work or school and limit contact with others. Patients are also asked to avoid touching their eyes, nose or mouth through which germs spread.

    What should one do if getting sick?

    Patients are recommended to seek emergency medical care if experiencing any of the following warning signs:

    In children, emergency warning signs that need urgent medical attention include: fast breathing or trouble breathing, bluish skin color, not drinking enough fluids, not waking up or not interacting, being so irritable that the child does not want to beheld, flu-like symptoms improve but then return with fever and worse cough, fever with a rash.

    In adults, emergency warning signs that need urgent medical attention include: difficult breathing or shortness of breath, pain or pressure in the chest or abdomen, sudden dizziness, confusion, severe or persistent vomiting.

    Can people get swine influenza from eating or preparing pork?

    No. Swine influenza viruses are not spread by food. People cannot get swine influenza from eating pork or pork products. Eating properly handled and cooked pork products is safe.