CMV contamination can be observed everywhere however clinical manifestations can rarely be seen. The disease-producing agent is pathogenic to man alone so its cultivation in vitro is only possible in human cell cultures, as no experimental animal is susceptible to the infection. CMV0infections are generally recorded with infants under two and elderly people which is accounted for by a disturbed or inadequate immunological response. Local and generalized lesions can far more often observed with patients having neoplastic processes, AIDS, after organ transplantation or with patients who take steroids. The infectious agent can be transmitted through placenta, by contact, while the fetus is advancing through the generative passage, through breastfeeding, blood transfusion or intercourse. Some experts believe that there can be airborne transmission of CMV or through urine. Perinatal contamination can be observed with 1% neonates, often with subclinical manifestations. In some cases, though not very often, the disease runs a grave course and has a lethal outcome. Typical of the acute form are lesions of many internal organs including encephalon, kidneys, liver and hemopoietic organs. The typical lesion in the subacute form is atypical interstitial pneumonia.