Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Croup ?
    ### Response:
    Croup is an inflammation of the vocal cords (larynx) and windpipe (trachea). It causes difficulty breathing, a barking cough, and a hoarse voice. The cause is usually a virus, often parainfluenza virus. Other causes include allergies and reflux.    Croup often starts out like a cold.
    