The reasons for cytomegalovirus positivity are as follows: 1. Previous history of recessive or dominant cytomegalovirus infection: If the cytomegalovirus IgG is positive, it only suggests a previous history of recessive or dominant cytomegalovirus infection; 2. Recent cytomegalovirus infection: Serum cytomegalovirus IgM is a retrospective indicator of recent cytomegalovirus infection, and if cytomegalovirus IgM is progressively elevated within a short period of time, it suggests that the patient has a recent cytomegalovirus infection. If the cytomegalovirus IgM is progressively elevated within a short period of time, it suggests that the patient has a recent cytomegalovirus infection. Among viral infections, cytomegalovirus infection is more common and is a common herpesvirus with a positivity rate of 30%-97% in human sera. Cytomegalovirus infection in immunocompetent people usually presents as a short period of fever or asymptomatic, after which cytomegalovirus presents a lifelong latent state in many cells and becomes a store for reactivation, and carriers become susceptible. When the body is in good immune status, cytomegalovirus is mostly recessive infection.