Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Cytomegalovirus Infections ?
    ### Response:
    Cytomegalovirus (CMV) is a virus found around the world. It is related to the viruses that cause chickenpox and infectious mononucleosis (mono). Between 50 percent and 80 percent of adults in the United States have had a CMV infection by age 40. Once CMV is in a person's body, it stays there for life.
    