Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) H1N1 Flu (Swine Flu) ?
    ### Response:
    Swine flu is an infection caused by a virus. It's named for a virus that pigs can get. People do not normally get swine flu, but human infections can and do happen. In 2009 a strain of swine flu called H1N1 infected many people around the world.    The virus is contagious and can spread from human to human.
    