CMV, which stands for cytomegalovirus, is a very common virus, and by adulthood, most people have been exposed to it, almost always without any symptoms. CMV is spread by person-to-person contact (kissing, sexual relations, bodily fluids). For example, it can spread if someone touches fluids from an infected individual, and then accidentally touches their own mouth. This is why hand-washing is so important. A common source of CMV is small children, so day-care workers and teachers are at increased risk for CMV exposure.

CMV is a concern because an infection during pregnancy can allow the virus to spread to the developing fetus, and can lead to birth defects such as deafness, blindness or mental retardation. One in 750 babies in this country is born with or later develops disabilities due to CMV infection passed from their mother during childbirth.

There is no vaccination and no treatment (except in severe cases). Precautions include: frequent hand washing, especially when around young children; avoid mouth-to-mouth kissing; do not share any cups or silverware. A blood test can be done to check for existing immunity. More than 50% of women are already immune to CMV. 


Pet mice can harbor a virus called LCMV (lymphocytic choriomeningitis virus). There may be no signs or symptoms in the mouse, yet this infection can be transmitted to humans. During pregnancy this type of infection can potentially harm the fetus (miscarriage, blindness, cerebral palsy, mental retardation). For this reason, pregnant women are advised not to handle pet mice, hamsters or other rodents. This is an extremely rare infection, and is mentioned here merely for the sake of completeness.