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Cytomegalovirus (CMV)

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General Information

•· Between 50% and 80% of adults in the United States are infected with CMV by 40 years of age

•· CMV is the most common virus transmitted to a pregnant woman's
unborn child

•· Approximately 1 in 150 children is born with congenital CMV infection

•· Approximately 1 in 750 children is born with or develops permanent disabilities due to CMV

•· Approximately 8,000 children each year suffer permanent disabilities caused by CMV

•· Congenital CMV (meaning present at birth) is as common a cause of serious disability as Down syndrome, fetal alcohol syndrome, and neural tube defects

About the Virus

· CMV is found throughout the world in all geographic and socioeconomic groups, but, in general, it is more widespread in developing countries and in areas of lower socioeconomic conditions

· CMV is a member of the herpesvirus family, which includes the herpes simplex viruses and the viruses that cause chicken pox (varicella-zoster virus) and infectious mononucleosis (Epstein-Barr virus)

· CMV is found in body fluids, including urine, saliva (spit), breast milk, blood, tears, semen, and vaginal fluids

· Once CMV is in a person's body, it stays there for life

· Most CMV infections are "silent," meaning they cause no signs or symptoms in an infected person

· CMV can cause disease in unborn babies and in people with a weakened immune system

Transmission and Prevention (How people become infected with CMV)

•· Transmission of CMV occurs from person to person, through close contact with body fluids (urine, saliva (spit), breast milk, blood, tears, semen, and vaginal fluids), but the chance of getting CMV infection from casual contact is very small.

•· In the United States, about 1%-4% of uninfected mothers have primary (or first) CMV infection during a pregnancy.

•· 33% of women who become infected with CMV for the first time during pregnancy pass the virus to their unborn babies.

•· No actions can totally eliminate all the risks of getting CMV, but there are simple measures that can reduce spread of the disease.

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, fatigue, and swollen glands. But these are also symptoms of other illnesses, so most people don't know it when they get CMV.

Most babies born with CMV (in other words congenital CMV) never develop symptoms or disabilities. When babies do have symptoms, some can go away but others can be permanent.

Examples of symptoms or disabilities caused by congenital CMV:

Temporary Symptoms	Permanent Symptoms or Disabilities
Liver problems Spleen problems Jaundice (yellow skin and eyes) Purple skin splotches Lung problems Small size at birth Seizures	Hearing loss Vision loss Mental disability Small head Lack of coordination Seizures Death

In some children, symptoms do not appear until months or years after birth. The most common of these late-occurring symptoms are hearing loss and vision loss. Children with congenital CMV are more likely to have permanent disabilities and symptoms that get worse if they had symptoms of CMV infection at birth. But, some children who appear healthy at birth can develop hearing or vision loss over time due to congenital CMV. For this reason, if you know your baby was born with CMV, it is important to have his or her hearing and vision tested regularly.

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.

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.

Guidelines for Clinicians

American College of Obstetricians and Gynecologists (ACOG). Perinatal viral and parasitic infections. Washington (DC): ACOG; 2000 Sep. 13. (ACOG practice bulletin; no. 20). 131 references Read the full text guidelines for clinicians

Reference

Effect of ganciclovir therapy on hearing in symptomatic congenital cytomegalovirus disease involving the central nervous system: a randomized, controlled trial. J Pediatr. 2003 Jul;143(1):16-25. Read the Medline Abstract of this paper

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.

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EditText of this page (last edited December 12, 2009)