Cytomegalovirus is a herpesvirus groupp DNA virus. Also called cellular inclusion virus, it has huge intranuclear inclusions due to the enlargement of infected cells. CMV has a typical herpesvirus morphology, and its DNA structure is also similar to HSV, but 5% larger than HSV. ELISA for detection of IgM antibodies and IgG antibodies is suitable for early infection and epidemiological investigation. IgG antibodies persist lifelong and IgM antibodies are associated with acute infection. PP65 protein is a capsular phosphoprotein of HCMV and is expressed both early and late in the HCMV replication cycle. The PP65 protein appears in the nucleus immediately after HCMV enters the host cell, and relocates to the cytoplasm later in infection. PP65 protein can appear in peripheral blood lymphocytes, monocytes, polymorphonuclear leukocytes and vascular endothelial cells with 6~24 hours after HCMV infection, indicating that PP65 protein is an important indicator for the early diagnosis of active HCMV infection. Therefore, the detection of PP65 antigen is important in early active HCMV infection.