Distribution and Incidence

Serologic studies show that cytomegalic inclusion disease has a worldwide distribution. It remains asymptomatic despite prolonged shedding of the virus at periodic reactivation but is not highly communicable. Presumably the virus is spread mainly by contact with oral secretions because it is shed from the salivary glands, and cultures from pharyngeal lymphoid structures commonly are positive. The virus has been isolated from urine, breast milk, semen, and cervix uteri, and consequently the infection may be a sexually transmitted disease.

The most serious aspect of CID is its role as a prenatal disease. Even though the mother is asymptomatic and immune, transmission of the virus to the fetus does occur. Recurrence of infection is the most probable explanation for prenatal infection although, of course, primary infection may occur during pregnancy, and there is evidence suggesting that infection in the offspring is more serious under such circumstances than when infection takes place because of recurrence in a mother protected by antibodies. A recent study has shown that children infected in a day-care center may be the source of infection for pregnant mothers.

With a disease spread mainly by oral secretions, a higher incidence is to be anticipated in those living in crowded and unhygienic surroundings. For example, 100 percent of the women in Tanzania have antibodies by the time they reach childbearing age. Other studies show seropositivity in 50 to 80 percent of children in boarding schools and orphanages in England as compared to 10 percent to 20 percent in children of the same age attending day schools. In Puerto Rico, between 70 and 80 percent of adults have the antibodies, whereas in London the figure is only 50 to 60 percent. J. A. Hanshaw has pointed out that studies in the United States and the United Kingdom show that from 0.2 to 7.5 percent of newborns are virus positive, making this disease the most common fetal infection. In the United States, the complement-fixing antibody is present in 5 to 25 percent of infants 8 to 24 months of age. In a study of the prevalence of cytomegalovirus excretion in 244 children aged from less than 1 year to 4 years in five day-care centers of a southern city of the United States, each child was tested for viral isolation by mouth swab and urine sample. It was found that 49 percent, 40 percent, 32 percent, 13 percent, or 9 percent of children, depending on the center, were excreting virus. Of the workers at the centers, 50 to 100 percent had antibodies to the virus, as did 56 to 88 percent of the parents.

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