CMV (Cytomegalovirus)

Cytomegalovirus

CMV is short for cytomegalovirus. You probably aren’t familiar with this long name, but all of us, usually without knowing it, are infected with CMV at some point in our lives. This viral infection rarely produces illness, but when it does—in newborns, AIDS patients, and transplant recipients—it can be devastating.
Scientists discovered cytomegalovirus in 1956. CMV, related to the herpes family of viruses, is the largest and most complex virus to infect humans.

How Do You Get It?

You catch CMV from close, intimate contact with infected urine; saliva; respiratory, vaginal, or cervical secretions; breast milk; or semen. It can be sexually transmitted, but most people get CMV through close household contact. Poor people are much more likely to be infected as young children, probably because they live in crowded conditions.
Babies get it from their mothers before birth, during delivery, or in the first few weeks of life. The baby is infected during pregnancy if its mother has either a first-time CMV infection or a reactivation of a past one.
Women who have toddlers attending child care are often infected. CMV transmission is rapid in these places because urine and saliva are passed from child to child on dirty hands. Young children rarely have symptoms, but they excrete the virus in their urine and saliva for months to years. Anyone working in child care or in any area with lots of young diapered children is exposed to CMV.
It is often transmitted from blood transfusions because so many people, including blood donors, have CMV infections with no symptoms.
Most people are infected with CMV before they reach adulthood, but very few people experience any symptoms or signs of illness. People with AIDS and organ transplant recipients are at highest risk for serious CMV infection—either pneumonia or retinitis, an eye infection. Often, their own latent CMV infections will reactivate as their immune systems either weaken or are suppressed by drugs to prevent organ rejection.
People who need organ transplants are tested for antibodies to CMV. Doctors will try to match CMV-negative organ donors to CMV-negative organ recipients. But a match isn’t always possible and the CMV-negative organ recipient faces a risk of serious CMV infection from the transplanted organ weeks to months later. To prevent this, the doctor will give the transplant recipient an injection of CMV antibody.
CMV-negative organ recipients who need blood transfusions will receive CMV-negative blood. This blood is hard to come by and is saved for people who really need it. If no CMV-negative blood is available, the blood can be filtered to remove the cells containing CMV. Otherwise, transplant patients may become ill if they receive CMV-infected blood.

How Do You Know If You Have It?

Babies. Babies infected before birth who become sick with CMV have symptoms affecting many major organs including the liver, brain, eyes, and lungs. The baby may suffer from convulsions, lethargy, a rash that looks like tiny red pinpoints on the skin, and breathing problems. Surviving babies often have such permanent damage as mental retardation, small brain or water on the brain (micro- or hydrocephalus), hearing loss, eye inflammations, poor coordination, and liver disease.

Children. Young children have few, if any symptoms. They may experience a mild cold- or flulike illness with fever, but you can’t tell it apart from any other mild viral illness.

Adults. Very few adults, including pregnant women, have any symptoms. Symptoms will be so mild—achiness, a low fever, sore throat—that you won’t be aware you are sick.

Tests

Because the virus is excreted in blood, urine, saliva, cervical secretions, and breast milk, CMV can be grown in any of these samples. It is not difficult to grow the virus, and the test is available in most large hospital and commercial labs. The virus grows slowly, however, and you may wait from two to six weeks for results.
You can also have your blood tested for the CMV antibody. If you have the antibody, you’ve been previously infected with CMV, but this test won’t tell whether the virus is present in your blood, urine, or saliva.
Newborns with possible congenital CMV infection must have virus cultured from their urine, nose, eyes, or spinal fluid to confirm CMV as the cause of illness.

How Sick Will You Be?

Babies. Almost all babies infected before birth are perfectly normal. Only about 10 percent of babies infected before birth are sick, and of these, 20 to 30 percent may die. Most survivors will have permanent damage. Some long-term studies suggest that a small number of apparently normal but CMV-infected babies at birth may have problems later in life. Congenital CMV has been linked to hearing loss and learning disabilities in children.

Children. Young children may have a mild cold or fever for a few days when first infected
with CMV.

Adults. CMV causes no signs or symptoms of illness in most adults. It will, however, cause an illness similar to mono in about ten percent of young adults.

Incubation Period

Information about the incubation period varies, and it is not well determined. Illness following transfusion may begin from three to eight weeks after receiving the infected blood. Babies born with congenital CMV may show symptoms from three to eight weeks after birth.

Infectiousness

Babies infected before birth excrete the virus on and off for years and are infectious during this time. Young children are infectious from six months to two years old. Adults are infectious for only a few months.

Immunity

Once you are infected, the virus remains latent in your body, just like other herpes viruses, and can be reactivated later in life under periods of stress or weakened immunity.

Complications

CMV can cause serious pneumonia, eye infections, and hepatitis in AIDS patients and anyone with a suppressed immune system, especially transplant recipients.

How Do You Treat It?

There is no cure for congenital CMV because the virus damages the baby before birth. Antiviral drugs cannot undo this damage once the baby is born. Doctors have good results with two antiviral drugs—ganciclovir (Cytovene) and foscarnet (Foscavir)— for treating and curing CMV disease in AIDS patients. Both these drugs are used to treat CMV retinitis and must be given by IV.
Nursing Care
Babies with congenital CMV need hospital care. Nursing care will depend on which organs the virus has damaged. Transplant patients and AIDS patients also need hospital care. Patients with serious CMV pneumonia require intensive care.

How Do You Prevent It?

In most cases you can’t prevent CMV, and you wouldn’t even want to. It’s best to be infected when you are young to reduce the risk of getting it for the first time during pregnancy.
Pregnant women who get CMV infection ma pass the virus along to their unborn baby. How can you prevent this? Unfortunately, I can’t offer any easy answers.
One expert suggested that pregnant mothers with children younger than two who attend group child care should avoid intimate contact with their toddlers during the first six months of pregnancy. I find this utterly unrealistic. But you can make a point of washing your hands well after changing diapers and wiping noses. Disposable wipes are handy when frequent running to a sink becomes impossible.
Pregnant nurses at the Children’s Hospital of Philadelphia had to do their best to avoid CMV. We advised them to assume that all babies and toddlers were shedding CMV in their urine and to use care when handling urine and saliva. Some wore gloves while others preferred to wash their hands carefully after handling a young patient. If you are pregnant and work with small children, or have a toddler attending day care, you can request a test for CMV antibodies when you begin prenatal care. Babies born to mothers with prior immunity are at less risk of congenital CMV infection.
In the future, we hope to learn more about why some babies who are infected with CMV become sick while most others don’t, and we will likely develop better medicines to fight this infection. In the meantime, strange as it seems, the best protection is to be infected young.