Any of several viruses in the herpes family. Active infection produces enlarged cells enclosing foreign matter. Most prevalent in crowded, poor communities, it is transmitted by sexual contact or infected body fluids. It rarely causes serious illness in healthy adults; however, it can lead to serious consequences, including blindness, in those with depressed immune systems. In newborns, even without spleen and liver enlargement (10percnt of cases), CMV is the most common infection and a major cause of congenital deafness; it may also induce retardation and blindness. There is no effective treatment.

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