Cytomegalovirus (CMV) is a common virus in the herpesvirus family. Fifty percent people have been infected by young adulthood and up to 85% by 40 years of age. Peaks of infection occur in children under 2 years age, and during adolescence. Once a person becomes infected, the virus remains alive but usually inactive (dormant) within that person’s body for life. It is rare for a person to get symptoms after the initial infection unless their immune system is weakened by severe illness and treatments (e.g. for cancer). Reactivation can occur during pregnancy in women who have had infection previously, with a very small risk of transmission of CMV to the unborn baby.
