Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Cold Sores ?
    ### Response:
    Cold sores are caused by a contagious virus called herpes simplex virus (HSV). There are two types of HSV. Type 1 usually causes oral herpes, or cold sores. Type 1 herpes virus infects more than half of the U.S. population by the time they reach their 20s. Type 2 usually affects the genital area     Some people have no symptoms from the infection.
    