Department of Pediatrics

What is CMV?


Frequently Asked Questions


Answers to your most frequently asked questions regarding the facts of CMV. Download or print the National CMV Registry brochure in English or Spanish.


What happens in the body during a CMV infection?

When CMV causes an infection for the first time, it is called a primary infection. Just as with all infections, the body begins to fight CMV by producing antibodies and immune cells. While there is an active infection in the body, CMV will be excreted or shed in body fluids. After infection, however the virus remains in the body in a latent or inactive state, usually for life. CMV antibodies will be present for life as well. Like other viruses in its family, CMV can reactivate (act like a new infection). This type of infection is a recurrent infection and may occur at any time, but especially when the immune system becomes altered or weakened. When reactivation occurs, CMV antibody levels may increase and viral shedding may reoccur.

What are usual signs and symptoms of acquired CMV infection?

When a person is infected with CMV any time after birth, it is known as an acquired infection. In normally healthy children and adults, CMV infection is usually not a concern. Ninety percent of the time it will not produce any signs or symptoms of infection. However, occasionally a flu-like or mononucleosis type of illness may occur and produce symptoms such as fever, sore throat, fatigue and swollen glands. In persons with a weakened immune system, such as patients who are infected with HIV, organ/bone marrow transplant recipients, chemotherapy/radiation patients, and people on steroid therapy, the signs and symptoms of CMV infection can be serious. Signs and symptoms can occur when an old CMV infection reactivates or when the person catches the virus for the first time. CMV infection in people with a weakened immune system puts them at risk for pneumonia, retinitis (an infection of the eye that can cause blindness), hepatitis (inflammation of the liver), esophagitis and colitis (gastrointestinal diseases), meningoencephalitis (an infection of the brain and the fluid that surrounds it), and even death.

How common is CMV in newborns?

CMV is the most common congenital infection that is passed from mother to unborn baby. Of the estimated four million infants born each year in the United States, approximately one percent will be congenitally infected with CMV. Most (90 percent or about 36,000 infants each year) of the congenitally infected infants will be symptom-free; however, the remaining ten percent (about 4,000 infants each year) may have one or multiple abnormalities.

How do you make a diagnosis of congenital CMV infection?

The diagnosis of congenital CMV infection is confirmed by isolating (growing) the virus from urine, saliva, or tissue that is collected during the baby's first three weeks of life. Urine usually is tested because it contains the highest concentration of the virus. A positive viral culture collected beyond the three-week period but within the first year of life should be considered a possible congenital CMV infection, but also may be an acquired CMV infection. The three-week period is important because after this time CMV can be isolated from babies that were infected during delivery or just after birth (for example, through breast milk). Unlike congenitally infected babies, most infants who acquire CMV during or after birth do not appear to be at risk for physical and mental disabilities.

What are signs and symptoms of congenital CMV disease?

Signs and symptoms of congenital CMV infection that are observed at birth include small head size (microcephaly), small body size, little red spots under the skin (petechiae), enlarged liver (hepatomegaly), enlarged spleen (splenomegaly), yellow color of skin and eyes (jaundice), low blood count (anemia and/or thrombocytopenia), pneumonia, seizures, abnormal muscle tone, calcium deposits in the brain (intracranial calcifications), vision loss, and hearing loss. Although some of these conditions may resolve, many children will have life-long disabilities of varying degrees. Possible disabilities associated with congenital CMV disease are deafness, blindness, physical and motor impairment, seizure disorder, developmental differences and learning delays.

What problems are associated with a "silent" CMV infection?

The majority of infants born with congenital CMV infection have a "silent" or symptom-free infection. Because these infants have no symptoms or abnormalities due to CMV at birth, the infection often goes unnoticed and undocumented. Unfortunately, they do not go totally unharmed by the CMV infection. Between 10-15 percent of all children born "silently infected" with CMV will develop varying degrees of hearing loss shortly after birth or during childhood. It is possible these children also may rarely experience vision problems or developmental and learning differences.

What are the chances my unborn baby has CMV?

The effect of CMV on the unborn baby may be serious when a woman catches the virus for the first time while she is pregnant. Between one percent and four percent of healthy women will catch CMV for the first time while they are pregnant (primary infection). Fewer than half (about 40 percent) of these women will pass the virus to the fetus, and only ten percent of the infected infants will have symptoms or abnormalities at birth. Almost always less severe are congenital CMV infections caused by a mother's recurrent CMV infection. When a woman previously infected with CMV becomes pregnant, it is possible for her to pass the virus to her unborn child through a recurrent infection. However, fewer than one percent of pregnant women who have CMV prior to pregnancy may experience a recurrent infection, and fewer than one percent of those recurrent infections will result in a baby being born with problems associated with CMV infection. See the chart.

When a diagnosis of congenital CMV has been made, what type of follow-up is recommended?

As with any newborn, regularly scheduled follow-up visits with the child's primary pediatrician or family doctor are advised. At birth, he or she should have baseline laboratory tests to determine what organs in the body have been affected by the virus. These tests include complete blood count, platelet count, and liver function tests. If laboratory results are abnormal, follow-up testing should be conducted. Also at birth, to see if the virus has damaged the central nervous system, children with congenital CMV infection should have a computerized tomography (CT) scan of the brain, an eye exam by an ophthalmologist, and a hearing test. Thereafter, at least annual hearing and visual exams are recommended. Because a child with congenital CMV infection may have special needs, her or his growth and development should be followed carefully. Also, unless there is a specific contraindication known, children with congenital CMV infection should receive the routine immunizations recommended for all children.

My child has been diagnosed with congenital CMV infection. When should his hearing be tested?

A child born with probable or confirmed CMV infection should have a hearing test done shortly after birth. Sometimes when a hearing test is warranted, a hearing screen is performed. Although a hearing screen is better than no test at all, a comprehensive hearing evaluation called acoustic brainstem response is the preferred testing instrument for infants and small children. An ABR is a reliable hearing test that is performed by an audiologist. Ask your pediatrician or family practitioner to help you schedule an appointment for the test. It is important to have your child's hearing checked as soon as possible. Early detection of a hearing impairment is vital so that intervention and referral can be made as needed. Children with hearing loss are at risk for delayed speech and language development. Early identification of any hearing loss and appropriate intervention will help to ensure that your child has every opportunity to reach his or her full potential and has the best quality of life.

Will my child's hearing loss get worse?

The most common disability associated with congenital CMV infection is hearing loss that is almost always progressive (worsens over time). Therefore, careful follow-up with an audiologist annually is recommended to monitor for changes. Early detection of hearing loss and proper intervention improves a child's ability to keep pace with developmental milestones, especially language development. Children with a significant hearing loss may benefit from hearing aids or other devices (check with an audiologist). Unfortunately, there is no medical treatment available at this time to prevent or lessen the effects of the hearing loss associated with congenital CMV infection. Cochlear implants (a mechanical device surgically inserted into the inner ear to help hearing) are available for some children with deafness due to congenital CMV.

Should I find out if my child is still shedding the virus?

CMV is a common virus that is shed by many young children, not just those who have congenital CMV infection. Most children who are congenitally infected with CMV will shed the virus through toddler and preschool ages. Infants and children who acquire CMV after the newborn period also may shed CMV for a prolonged period of time. The virus will affect each child differently, and the length of viral shedding may vary. Viral shedding can range from just a few months to eight years of age, and possibly longer. It is not necessary to routinely determine if your child still has the virus active in the urine or saliva because its presence does not appear to influence or predict problems. Furthermore, schools, teachers, and therapists should not require your child to be tested for CMV shedding before being accepted into a program. And they may not deny your child access to education because of the diagnosis of congenital CMV infection.


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