CMV is a common virus and infects people of all ages. It spreads via direct contact with body fluids such as semen, saliva, breast milk, vaginal fluid, placenta, and blood. Thus individuals who visit or work in childcare facilities, patients who get blood transfusions, people who have many sex partners, and recipients of CMV mismatched organ or bone marrow transplants are all at risk for CMV infection. Congenital CMV transmission from a woman with acute CMV infection during pregnancy causes neurological problems and deafness in about 8000 infants in the United States each year. CMV comes in a variety of genetically different strains. Differences in genotypes may be linked to virulence differences. It is possible to become infected with more than one strain of CMV, and this has been documented in organ transplant patients. Congenital CMV infection in infants born to CMV-positive moms might be due to dual infection.