Cytomegalovirus, or CMV, is a common virus that can infect people of all ages. According to the Centers for Disease Control and Prevention (CDC), over half of adults have been infected with CMV by the age of 40, and at least one-in-three children have already been infected by the age of five. Most of the time, the virus causes only minor symptoms following infection, and often it causes no symptoms at all. However, CMV infection can cause health issues for those with a weakened immune system, including transplant recipients. CMV can also cause infection of an infant before birth. When acquisition of the virus occurs in utero, it leads to congenital CMV infection.