The difference between cytomegalovirus IgG and IgM lies in the cytomegalovirus infection status: the former suggests previous infection; the latter suggests recent infection. IgG is the most important type of antibody in the human body and plays a major role in immunoprotection. Positive cytomegalovirus IgG suggests previous infection with the virus and the persistence of antibodies in the body, which have a protective effect; however, it does not indicate the presence or absence of cytomegalovirus infection. IgM is the first antibody produced when the body is stimulated. Cytomegalovirus IgM positivity suggests recent infection and the presence of active cytomegalovirus infection in the body, which requires timely antiviral treatment according to the examination. Cytomegalovirus IgM usually disappears after acute infection. If you have any related symptoms, please consult the doctor and follow the medical advice.