Most healthy children and adults infected with CMV have no symptoms and may not even know that they have been infected. Others may develop a mild illness; symptoms may include fever, sore throat, rash and fatigue.
Other symptoms, such as swollen glands, liver or spleen, may sometimes be present. However, these can be symptoms of a wide range of conditions, not just CMV. Always talk to your doctor or midwife if you have concerns.
A blood test can tell if you have an active CMV infection or have had a previous infection. Doctors can diagnose a maternal primary CMV infection (catching CMV for the first time) by testing for Immunoglobin M (IgM) and Immunoglobin G (IgG) antibodies and performing an “avidity” test, which checks how tightly the IgG binds to CMV. By analysing levels of these antibodies and the avidity test, an estimate of the timing of CMV infection can be made. These results will be interpreted by a virologist, as they are not always straight-forward. Sometimes your midwife or doctor may ask you to have further blood tests done a few weeks later to help interpret the results of your tests.
The timing of CMV infection is associated with the risk that the baby will be affected by congenital CMV. If CMV infection is contracted in the first trimester, the risk of long-term problems is estimated at less than 1 in 100 and the risk in the third trimester is negligible. Whilst the risks in the later stages of pregnancy are thought to be very low, the studies that report these findings have only followed up infants for the first few years of life, and longer-term studies are yet to report.
As the risks are highest around conception and early pregnancy, it is particularly important that women planning pregnancy or in the early stages of pregnancy take particular care to reduce the risks of catching CMV.
Even if you have had CMV before, it is still possible to catch a different strain. It is therefore important for all pregnant women, and those planning a pregnancy, to follow simple hygiene precautions even if they have had CMV before – nobody is ‘immune’.