Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Chickenpox ?
    ### Response:
    Chickenpox is an infection caused by the varicella-zoster virus. Most cases are in children under age 15, but older children and adults can get it. It spreads very easily from one person to another.    The classic symptom of chickenpox is an uncomfortable, itchy rash.
    