In a healthy adult or child, cytomegalovirus (CMV) infection can cause mild fever, fatigue, sore throat, swollen glands, and other minor symptoms. Most adults and many children have no symptoms. A healthy person's immune system will usually prevent the virus from causing illness. Healthy people infected with CMV usually do not require medical treatment.
Less commonly, CMV infection can also cause mononucleosis, or "mono" for short. Mononucleosis and typical CMV infections share many symptoms, but individuals with mononucleosis can also experience enlarged spleen and liver. Mononucleosis is more commonly caused by infection with Epstein-Barr virus, a related human herpes virus.
Dangers to Women who are Pregnant or May Become Pregnant
A mother's CMV infection can pass through the placenta to the fetus and may cause intellectual and motor disabilities, such as cerebral palsy, seizures, and impaired hearing and vision. The risk is highest if the mother is infected in the first trimester of pregnancy, and if the CMV infection is a primary one (i.e., the first time the mother is infected with the virus).1
Vaccines and Treatment
Research into a CMV vaccine is ongoing; however, there is currently no vaccine available or proven treatment for adults with a CMV infection. A healthy person's immune system will usually prevent the virus from causing illness. Healthy people infected with CMV usually do not require medical treatment.
Testing for CMV Infection
Although several CMV tests exist, the Centers for Disease Control and Prevention (CDC) does not recommend that doctors routinely test pregnant women for CMV infection because laboratory tests cannot predict which developing babies will become infected with CMV or have long-term health problems.
Blood tests can check for CMV antibodies. Positive test results indicate the person currently has or previously had a CMV infection; however, this does not necessarily mean the person is infectious. In addition, most blood tests cannot determine the CMV strain responsible for past or current infection, and there is no consensus on these tests' utility.
Other lab tests (e.g., viral culture or polymerase chain reaction) on saliva, urine, or blood can be used to diagnose current infection. In addition to common body fluids, a mother's cervical secretions or breastmilk can also be tested, if needed.
CMV Immunity and Latency
CMV comes in many different strains. After being infected by a specific CMV strain, a person develops immunity to that strain, but this immunity does not protect against other CMV strains. While nearly 50% of U.S. women have had at least one CMV infection before a pregnancy, they are still vulnerable to CMV. Only about 25% of babies born with CMV infections had mothers who became infected for the first time during pregnancy.2
As with other herpes viruses, CMV stays in a person's body for life. It can become dormant and reactivate at a later time, including during pregnancy. While it is possible to pass a reactivated infection to the fetus, a mother is more likely to pass the virus to her baby during a new CMV infection.
1 Cytomegalovirus (CMV) and Congenital CMV Infection. (2018). Centers for Disease Control and Prevention, U.S. Department of Health and Human Services.
2 Cytomegalovirus (CMV) and Congenital CMV infection: Clinical Overview. (2018). Centers for Disease Control and Prevention, U.S. Department of Health and Human Services.