Cytomegalovirus (CMV) : Part 2

by CDC

(Page 2 of 2)

CMV testing if you are planning a pregnancy

If you are planning to become pregnant, a CMV blood test can help you know how careful you must be to prevent CMV infection. If you test positive, you will know that there is little chance that your baby will be harmed by CMV. If you test negative, carefully follow the recommendations for preventing CMV infection before and during your pregnancy. Either way, it is always a good idea to follow the prevention guidelines because they will also help you avoid other infections.

CMV testing of your newborn

If you find out that you became infected with CMV for the first time during your pregnancy, you should make sure your baby is tested for CMV as soon as he/she is born. If you are concerned about congenital CMV for any other reason, you should also talk to your doctor about having your baby tested. This will let you know whether you should think about treating your baby for CMV infection. If your baby tests positive, you should also have his or her hearing and vision tested regularly. Most CMV-infected babies grow up with normal health, but if your child has delayed hearing or vision problems, early detection can help his or her development.

Diagnosis

There are several CMV tests that measure different things:

How can I know if I've ever been infected with CMV?

A blood test for IgG antibodies (special immune system proteins) is how your doctor can determine whether you've ever been infected with CMV. By itself, this test won't show whether you were infected during your pregnancy, nor will it tell you whether your fetus has been infected with CMV. If you test negative before your pregnancy, you should take special care to prevent CMV infection while you are pregnant. How can I know if I've been infected with CMV during my pregnancy?

New CMV infections can be found by doing testing for a type of antibodies ("IgG" antibodies) on blood samples taken at different times. If the first sample is negative and the second sample is positive, then you became infected with CMV sometime between the two samples. A new method, called IgG avidity testing, needs only one blood sample to show whether you have a recent CMV infection. However, this test is currently not commercially available in the U.S. In the past, a test for IgM antibodies (another immune system protein) has been done to try to detect recent infections. Because this test is often positive when there is no new CMV infection, it should not be used without the other tests.

How can I know if my fetus has been infected with CMV?

For these reasons, and because there are no safe and effective CMV drugs for pregnant women, we do not recommend routine screening to see if a fetus is infected with CMV. Blood tests are sometimes used to find women who have new CMV infections. These women have a high risk (about 1/3) of passing the virus to their fetus. Tests of amniotic fluid or fetal blood, along with ultrasound readings of women, often can identify which of these women passed the virus to their fetus. However, these tests are invasive and don't always correctly identify infected fetuses or fetuses who will have health problems.

How can I know if my newborn has congenital (meaning present from birth) CMV?

A newborn has congenital CMV if the virus can be found in their urine, saliva, or blood during the first 3 weeks after birth. Rather than detecting antibodies, tests must identify the virus itself. Congenital CMV cannot be diagnosed if the baby is tested more than 3 weeks after birth, since she/he could have been infected after birth. Babies infected after birth are not at risk for disabilities. If your baby has congenital CMV, you should have her hearing and vision tested regularly. Most CMV-infected babies grow up with normal health, but if your child has delayed hearing or vision problems, early detection can help his or her development.

Should I be tested for CMV if I am planning a pregnancy?

If you are planning to become pregnant, a CMV blood test (which tests for IgG antibodies - special immune system proteins) can help you know how careful you must be to prevent CMV infection. If you test positive, you will know that there is little chance that your baby will be harmed by CMV. If you test negative, carefully follow the recommendations for preventing CMV infection before and during your pregnancy. Either way, it is always a good idea to follow the prevention guidelines because they will help you avoid other infections as well.

Treatment and Vaccine

Scientists are working on CMV vaccines and are looking for other ways to prevent congenital (meaning present at birth) CMV. For now, there are no treatments for pregnant women whose fetuses might be infected with CMV. Current drugs that are effective against CMV have serious side effects and are not approved for use in pregnant women.

There is some evidence that ganciclovir, an antiviral drug, may prevent hearing loss in infants born with congenital CMV. However, this drug has serious side effects and was only tested in children with severe congenital CMV symptoms. If your child has symptoms of congenital CMV, you should consult with your doctor to decide whether to try treatment.

Vaccine Research

There is no available vaccine for preventing congenital (present at birth) CMV disease. However, a few CMV vaccines are being tested in humans, including live attenuated (weakened) virus vaccines and vaccines that contain only pieces of the virus. The Institute of Medicine has ranked the development of a CMV vaccine as a highest priority because of the lives it would save and the disabilities it would prevent. It may be a number of years before there is a Food Drug and Administration-approved CMV vaccine. Because CMV is not spread as easily as some other diseases, even a partially effective CMV vaccine will have a large impact on the congenital CMV disease epidemic.

About the Author

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The Centers for Disease Control and Prevention (CDC) is one of the 13 major operating components of the Department of Health and Human Services (HHS), which is the principal agency in the United States government for protecting the health and safety of all Americans and for providing essential human services, especially for those people who are least able to help themselves.