Cytomegalovirus infection. Computer illustration of human cells showing cytomegalic inclusion disease, a symptom of cytomegalovirus infection. Cytomegalovirus (CMV) particles invade cell nuclei, causing the appearance of darker bodies within them (inclusion bodies, often called 'owl's eye' inclusions) together with formation of multinucleated cells. The illustration shows the cell with two nuclei each containing CMV inclusion. CMV infection is common, and usually produces no symptoms. In some cases, however, it may lead to a disease resembling glandular fever (mononucleosis). In immunosuppressed patients, the disease is more serious. Also, pregnant women can pass the virus to their foetus, which can cause malformations and brain damage.