Cytomegalovirus infection



Definition

Cytomegalovirus (CMV) is a virus related to the group of herpes viruses. Infection with CMV can cause no symptoms or can be the source of serious illness in people with weak immune systems. CMV infection is also an important cause of birth defects.

Description

CMV is an extremely common organism worldwide. It is believed that about 85 percent of the adults in the United States have been infected by CMV at some point in their lives. CMV is found in almost all of the body's organs. It is also found in body fluids, including semen, saliva, urine, feces, breast milk, blood, and secretions of the cervix (the narrow, lower section of the uterus).

CMV is also able to cross the placenta (the organ that provides oxygen and nutrients to the unborn baby in the uterus). Because CMV can cross the placental barrier, initial infection in a pregnant woman can lead to infection of the developing baby.

Demographics

In the United States, about 40 to 60 percent of all adults in the middle- and upper-socioeconomic classes show antibody proof of prior infection with CMV; antibody proof is as high as 80 percent in adults in the lower socioeconomic class. Worldwide, about 0.2 to 2.2 percent of all babies are born with congenital CMV infection. Of those babies born with congenital CMV infection, about 10 percent to 20 percent ultimately suffer form hearing impairment , eye damage, or problems with intellectual or motor function.

Causes and symptoms

CMV is passed between people through contact with body fluids. CMV also can be passed through sexual contact. Babies can be born infected with CMV, either becoming infected in the uterus (congenital infection) or during birth (from infected cervical secretions).

Like other herpes viruses, CMV remains inactive (dormant) within the body for life after the initial infection. Some of the more serious types of CMV infections occur in people who have been harboring the dormant virus, only to have it reactivate when their immune system is stressed. Immune systems may be weakened because of cancer chemotherapy , medications given after organ transplantation, or diseases that significantly lower immune resistance like acquired immunodeficiency syndrome ( AIDS ).

In a healthy person, initial CMV infection often occurs without symptoms and is rarely noticed. Occasionally, a first-time infection with CMV may cause a mild illness called mononucleosis. Symptoms include swollen glands, liver, and spleen; fever ; increased white blood cells; headache ; fatigue; and sore throat . About 8 percent of all mononucleosis cases are due to CMV infection. A similar infection, though slightly more serious, may occur two to four weeks after receiving a blood transfusion containing CMV.

In people with weakened immune systems, CMV infection can cause more serious and potentially life-threatening illnesses. These illnesses include pneumonia and inflammations of the liver (hepatitis), brain ( encephalitis ), esophagus (esophagitis), large intestine (colitis), and retina of the eye (retinitis).

Babies who contract CMV from their mothers during birth rarely develop any illness from these infections. Infants born prematurely who become CMV infected during birth have a greater chance of complications, including pneumonia, hepatitis, decreased blood platelets.

However, an unborn baby is at great risk for serious problems when the mother becomes infected with CMV for the first time while pregnant. About 10 percent of these babies will be born with obvious problems, including prematurity , lung problems, an enlarged liver and spleen, jaundice , anemia, low birth weight, small head size, and inflammation of the retina. About 90 percent of these babies may appear perfectly normal at birth. Unfortunately, about 20 percent later develop severe hearing impairments and mental retardation . A 2003 report found that pregnant women 25 years of age and older who are immune to CMV are much less likely to pass the virus to their babies than younger women who have never been exposed to CMV.

Diagnosis

Body fluids or tissues can be tested to reveal CMV infection. However, this information is not always particularly helpful because CMV stays dormant in the cells for life. Tests to look for special immune cells (antibodies) that are directed specifically against CMV are useful in proving that a person has been infected with CMV. However, these tests do not give any information regarding when the CMV infection first occurred.

Treatment

Ganciclovir and foscarnet are antiviral medications that have been used to treat patients with weak immune systems who develop a serious illness from CMV (including retinitis). As of 1998, research was still being done to try to find useful drugs to treat newborn babies

An infected retina caused by a cytomegalovirus. (Photograph by Paula Ihnat. Custom Medical Stock Photo, Inc.)
An infected retina caused by a cytomegalovirus.
(Photograph by Paula Ihnat. Custom Medical Stock Photo, Inc.)
suffering from congenital infection with CMV. Antiviral drugs are not used to treat CMV infection in otherwise healthy patients because the drugs have significant side effects that outweigh their benefits. In 2003, researchers in Europe announced a new compound that appeared to be highly effective against CMV infections. The new drug acted earlier in the viral replication of the infection and showed promise; however, clinical trials were continuing.

Prognosis

Prognosis in healthy people with CMV infection is excellent. About 0.1 percent of all newborn babies have serious damage from CMV infection occurring while they were developing in the uterus. About 50 percent of all transplant patients develop severe illnesses due to reactivation of dormant CMV infection. These illnesses have a high rate of serious complications and death.

Prevention

Prevention of CMV infection in the normal, healthy person involves good hand washing. Blood products can be screened or treated to insure that they do not contain CMV. In 2003, a new high-dose prophylactic (preventive) treatment was being tested to reduce CMV risk in stem cell transplant recipients.

KEY TERMS

Cervix —A small, cylindrical structure about an inch or so long and less than an inch around that makes up the lower part and neck of the uterus. The cervix separates the body and cavity of the uterus from the vagina.

Congenital —Present at birth.

Placenta —The organ that provides oxygen and nutrition from the mother to the unborn baby during pregnancy. The placenta is attached to the wall of the uterus and leads to the unborn baby via the umbilical cord.

Resources

BOOKS

"Cytomegalovirus Infection." In Obstetrics: Normal and Problem Pregnancies. Edited by Steven G. Gabbe. London: Churchill Livingstone, 2002.

Pass, Robert F. "Cytomegalovirus." In Principles and Practice of Pediatric Infectious Diseases , 2nd ed. Edited by Sarah S. Long et al. St. Louis, MO: Elsevier, 2003.

Stagno, Sergio. "Cytomegalovirus." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.

PERIODICALS

Fowler, Karen B., Sergio Stagno, and Robert F. Pass. "Maternal Immunity and Prevention of Congenital Cytomegalovirus Infection." Journal of the American Medical Association (February 26, 2003): 1008.

"High-Dose Acyclovir May Reduce Cytomegalovirus Infection Risk." Virus Weekly (July 15, 2003): 16.

"Novel Compound Highly Effective Against Cytomegalovirus Infection." AIDS Weekly (November 25, 2003): 17.

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. Web site: http://www.cdc.gov.

March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. Web site: http://www.modimes.org.

Rosalyn Carson-DeWitt, MD Teresa G. Odle

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