Cytomegalovirus (CMV) is a very common virus that infects approximately one-half of all young adults in the United States. It rarely causes serious consequences except in people with suppressed or impaired immune systems or in infants, whose immune systems are still developing. The virus, a member of the herpes virus family, is found in saliva, urine, and other bodily fluids. Because it is often found in semen as well as in cervical secretions, the virus can be spread by sexual contact; it also can be easily spread by other forms of physical contact such as kissing. Day-care center staff for children under the age of 3 are at increased risk of CMV infection and should carefully wash their hands after changing diapers. Like other herpes virus infections, CMV is incurable; people are infected with it for life. Although the virus usually remains in an inactive state, it can reactivate from time to time.
In healthy adults, CMV usually produces no symptoms of infection. Occasionally, however, mild symptoms of swollen lymph glands, fever, and fatigue may occur. These symptoms may be similar to those of infectious mononucleosis.
The ELISA (enzyme-linked immunosorbent assay) test is commonly used to detect levels of antibodies (disease-fighting proteins of the immune system) in the blood. A number of other blood tests can suggest a diagnosis of CMV infection, but no blood test can reliably diagnose it. Although CMV can be isolated from urine or other body fluids, it may be excreted months or years after an infection; therefore, isolation of the virus from these fluids is not a reliable method of diagnosing recent infection.
Babies can be infected with CMV in the uterus if their mothers become infected with the virus or develop a recurrence of a previous infection during pregnancy. Although most babies infected with CMV before birth do not develop any symptoms, CMV is the leading cause of congenital infection in the United States. An estimated 6,000 babies each year develop life-threatening complications of congenital CMV infection at birth or suffer serious consequences later in life, including mental retardation, blindness, deafness, or epilepsy. Investigators supported by NIAID are currently studying how the virus interferes with normal fetal development and at which stages the fetus is most susceptible to infection. Congenital CMV is the most common cause of progressive deafness in children.
When CMV is acquired after birth, or if it reactivates, it can be life-threatening for persons with suppressed immune systems, such as those receiving chemotherapy or persons who have received immunosuppressant drugs for organ transplantation. Persons with HIV infection or AIDS may develop severe CMV infections, including CMV retinitis, an eye disease that can lead to blindness.
NIAID scientists are testing new antiviral drugs that might be effective against CMV infections. The antiviral drugs foscarnet and ganciclovir have been approved for treating people with AIDS-associated CMV retinitis.
There is no intervention to prevent CMV. Use of the male condom may reduce risk although virus in the saliva would be transmitted by kissing or oral intercourse. Some experts believe that primary or first-time exposure during pregnancy is a major cause of CMV infection in newborns. Infants infected before or just after birth are likely to be shedding CMV in saliva and urine, which can infect others. Hand washing and proper handling of diapers may reduce risk. Scientists are working to develop a vaccine and other methods to provide immunity to CMV and offer protection against severe disease.
SOURCE: National Institute of Allergy and Infectious Diseases
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