Cytomegalovirus (CMV): What It Is, Causes, Symptoms & Treatment

What is cytomegalovirus (CMV)?

Although few people have heard of cytomegalovirus, or CMV, many of us are carrying it at this very moment.

It's a common virus that's spread during sex, or in blood, urine, saliva, or breast milk; babies can also be infected with it before or during birth. Fifty to 80 percent of American adults have CMV by age 40, but the majority doesn't even know it. The reason is that in healthy adults, the virus usually causes no symptoms or problems at all. Once the virus (a cousin of the herpes virus) enters your body, it's there for life -- but most of us produce enough antibodies to keep it inactive.

Is it dangerous?

For the vast majority of people, no. Occasionally healthy children, teenagers, or adults develop what's called CMV mononucleosis when they're infected with the virus for the first time. This is characterized by a mononucleosis-like condition that goes away in two or three weeks.

In two groups of people, though, CMV can cause serious problems. These groups consist of people who have severely weakened immune systems and women who get infected for the first time during pregnancy.

CMV can strike anytime the immune system is under massive attack, as in the case of chemotherapy patients, people with AIDS, or organ transplant recipients (who must take drugs to suppress their immune response). In an ailing immune system, the dormant virus may become active and cause dangerous illnesses. If untreated, it can spread throughout the body, infecting organ after organ. It may cause respiratory problems, damage to the central nervous system, bleeding ulcers in the digestive system, and CMV retinitis, which can lead to blindness.

If a woman gets the virus for the first time while she is pregnant, CMV can also cause disease in fetuses and newborns. A woman who's healthy isn't at special risk of contracting CMV during pregnancy, but if this happens, the virus can be passed to the fetus through the placenta or in the birth canal. The baby then has a chance of developing congenital CMV disease, which can result in brain damage and other problems.

What are the symptoms of CMV?

Few people infected with CMV notice any symptoms, even when they first contract it. If you do have symptoms, they may take the form of swollen lymph nodes and some tiredness. CMV mononucleosis, however, can cause a two- or three-day fever, fatigue, a sore throat, and swollen glands.

What is the treatment?

If you get CMV mononucleosis, you won't require any treatment; the illness goes away by itself. People whose immune systems are compromised, on the other hand, are usually treated with the antiviral drug ganciclovir, which can sometimes cause nausea, a lowered testosterone level, and a decrease in the white blood cells called neutrophils. Ganciclover is also being used experimentally on babies with congenital CMV disease.

What can happen if the baby gets CMV disease?

If the baby contracts CMV after she's born, the consequences are rarely serious. But if she gets it in the womb or during birth and develops congenital CMV disease, she may be stillborn, premature, or born with neurological damage such as mental retardation, cerebral palsy, or deafness. Such a baby usually shows symptoms at birth, including small size, a small brain (a condition called microcephaly), eye problems, an enlarged liver and spleen, and extra fluid that puts pressure on the brain. In perhaps as many as 15 percent of infected newborns, though, there are no indications at birth; instead, speech and developmental difficulties, learning disabilities, or problems with hearing or sight appear later.

Is congenital CMV disease common in infants?

It's the most common viral infection in babies before birth, affecting about 1 in 150 babies born in the United States. Almost always, an infection occurs because the mother contracts CMV for the first time (the point at which it's most potent, because her body hasn't yet built up antibodies to it) during pregnancy. Since most women are already infected with CMV before their child-bearing years arrive, the risk that this will happen is small.

How can I protect my unborn baby from CMV?

Because so few women are first infected with the virus while they're pregnant, there's no screening process for pregnant women or those considering pregnancy. Some doctors believe that reports on CMV in the media have made people unnecessarily anxious about it, since a baby's actual chance of contracting congenital CMV is extremely slight.

If you're concerned, however, you can ask your doctor to do a blood test that shows the presence of CMV antibodies in your blood. The general theory is that a high level of CMV antibodies may indicate that you've recently been infected by the disease and shouldn't try to get pregnant till six months have passed. A low level may mean that you've had the infection for some time and it's okay to get pregnant. If you have no antibodies, then you've never been infected with CMV and must be extra careful to stay free of it during pregnancy. Prenatal tests of amniotic fluid can help indicate whether a fetus has been infected with the virus or not.

If I haven't already contracted CMV, how can I keep from doing so while I'm pregnant?

Here are a few guidelines:

• Practice good hygiene throughout your pregnancy. Young children tend to be more contagious than adults, since they're more likely to be experiencing their first CMV infection and to be shedding the virus in their bodily fluids. With that in mind, wash your hands carefully with soap and hot water after changing a diaper or coming into contact with saliva, urine, or the like.
• Don't share drinks, pipes, cigarettes, eating utensils, or food (like an ice cream cone).
• Use condoms to avoid contact with CMV carried in semen.
• If you develop an illness similar to mononucleosis during pregnancy, have yourself tested for CMV and get counseling about the possible risks to the fetus.
• If you need a transfusion during pregnancy and you're CMV-negative or unsure whether you have the virus, request "CMV-seronegative" blood or special blood filters to decrease the risk of CMV transmission.
• If you work in a daycare center, wash your hands carefully after contact with your young charges' urine or saliva. Avoid touching your mouth if you've handled a cup, pacifier, toy, or other object with saliva on it.

If my immune system is severely weakened, what can I do to protect myself?

Stay as healthy as possible in order to keep CMV from flaring up. Eat well, consider taking a daily multivitamin, and get plenty of exercise and rest. Report any new symptoms to your doctor, including "floaters" in the eye or weakened eyesight (these could be early symptoms of retinitis). If it turns out that you do have an active case of CMV, consult with your doctor about the best form of treatment.

References

Centers for Disease Control. CMV and Congenital CMV Infection.

Centers for Disease Control, National Center for Infectious Diseases. Cytomegalovirus Infection.

Centers for Disease Control. About CMV.