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Cytomegalovirus (CMV)

Medically reviewed by Last updated on Feb 8, 2024.

What is cytomegalovirus (CMV)?

Harvard Health Publishing

Cytomegalovirus (CMV) is a virus related to the herpes virus. It is so common that almost all adults in developing countries and 50% to 85% of adults in the United States have been infected.

Usually CMV is a mild disease that does not cause any serious problems in healthy children and adults. Most people get flu-like symptoms or an illness similar to mononucleosis, if they develop symptoms at all.

Being infected with this virus can be serious and even fatal in some people, however, including:

Women infected with CMV for the first time during pregnancy can pass the virus to their unborn babies in the womb. The virus can also pass from mother to baby in vaginal secretions during delivery and in breast milk after birth. The virus can pass from person to person through close personal contact, sexual contact, blood transfusion or organ transplantation.

Symptoms of CMV

There are three classes of CMV infection, each with different symptoms:


Up to 40% of babies born to women who are newly infected with CMV during pregnancy will become infected. Not all infected babies will have symptoms at birth. This type of CMV infection causes as much serious disability as Down syndrome, fetal alcohol syndrome and neural tube defects.

Newborns with CMV are likely to be born premature and at a low birth weight. Other possible problems include a small brain (microcephaly) or other nervous system disorders that can cause seizures, deafness, intellectual disabilities or death. This infection can cause the liver and spleen to become larger than normal, yellowing of the skin and eyes (from liver disease), and blood disorders. Newborns with CMV can have a rash that consists of small bruises called petechiae and larger bruises known as purpura.

A baby born to a mother who was already infected with CMV before she became pregnant is less likely to be born with CMV. Only 0.5% to 1.5% of such babies are infected (compared to 40% of babies born to mothers who were infected during pregnancy), and their problems tend to be less severe.

Healthy people

In most cases, healthy people who become infected with CMV usually develop minor symptoms or no symptoms at all. When symptoms occur, they are similar to the symptoms of mononucleosis:

The virus usually becomes inactive (latent or dormant) in healthy people without specific treatment. CMV is never completely cleared from the body, however, and can reactivate in situations such as immune suppression.

Immune-suppressed people

People who have had an organ or bone marrow transplant and those with AIDS can develop serious illness caused by CMV. Typically, latent virus from a previous infection (the original CMV infection may have occurred many years earlier) becomes active again because the person's immune system is weakened. People with weakened immune systems are at greater risk of becoming very ill if they never had CMV in the past and acquire a new infection.

Reactivated CMV infection can affect many parts of the body:

Diagnosing CMV

Doctors may order blood tests for babies with low birth weight, jaundice, small brains or other problems that can be associated with congenital CMV, but can also be caused by other things. The diagnosis needs to be confirmed by testing blood or tissue from the infant within three weeks of birth.

Young, healthy adults usually do not need to be tested because they do not need to be treated specifically for CMV. They usually recover over a period of weeks. In some instances, blood tests may be done to confirm the cause of the illness, since similar symptoms can be caused by Epstein-Barr virus (EBV) and even human immunodeficiency virus (HIV). Tests may also be needed to monitor blood levels and liver inflammation. Occasionally, ultrasound testing is needed to monitor the liver or spleen.

For people with HIV/AIDS who have a severely weakened immune system, or for people who have had an organ or bone marrow transplant, the diagnosis of CMV usually requires a detailed physical exam and blood tests. Depending on the symptoms, urine and stool samples may be tested. Sometimes, a biopsy of the affected organ, such as the lung or colon, is needed to confirm the diagnosis.

Expected duration of CMV

Disease progression in babies who are infected in the womb, during birth or through breastfeeding may vary a great deal. Some babies may die from the infection and some may have no long-lasting effects at all. Prognosis depends on many factors and these babies should be seen by a specialist.

Adults with a healthy immune system who are already infected with CMV can expect the virus to remain inactive. No further symptoms related to CMV are expected to develop.

A person with a weakened immune system who develops CMV-related disease (either primary infection or reactivation) will often need lengthy treatment. Improving the immune system is the best hope for combating any invading viruses.

Preventing CMV

Pregnant women who care for young children should:

If you are pregnant and work in a day care center, reduce your risk of getting CMV by working with children who are older than 2 and a half years of age, especially if you have never been infected with CMV or are unsure if you have been exposed.

In some cases, people with AIDS or those who have had an organ or bone marrow transplant may need to take medication to prevent CMV reactivation. If people with weakened immune systems need blood transfusions, they will probably receive blood that has had the white blood cells removed. This lowers the risk of infection.

Also, it is essential for people with HIV/AIDS who have extremely weakened immune systems to schedule regular eye exams to detect CMV early, even before symptoms develop. This can help to avoid the loss of vision.

Treating CMV

The treatment of babies infected with CMV depends on the type and severity of symptoms. Treatment should be provided by a specialist on a case-by-case basis.

Healthy people generally do not need any specific treatment for CMV.

Although there is no cure for CMV, organ transplant recipients, people with AIDS and others with immune disorders may need treatment to suppress the latent infection. Treatment for CMV may include trying to correct the underlying immune disorder. For example, experience in treating people with AIDS shows that when a person's immune system improves, CMV-related conditions can improve.

Drugs used to treat CMV include ganciclovir (Cytovene or Vitrasert), valganciclovir (Valcyte), cidofovir (Vistide) and foscarnet (Foscavir).

Side effects of ganciclovir and valganciclovir include the suppression of white blood cells (needed to fight infection), red blood cells (that carry oxygen) and platelets (that help the blood to clot). Because cidofovir and foscarnet can cause kidney damage, kidney function needs to be monitored carefully.

When to call a professional

A doctor should see your baby if he or she has yellow skin (jaundice), hearing problems, rash, fever, seizures or vomiting. If you are a healthy adult, call your doctor if you have severe abdominal pain, vomiting or fevers that last longer than 48 hours or if you have significant fatigue, sweats, chills or are losing weight.

If you have a weakened immune system, see a doctor if you have visual changes, mental changes, difficulty or pain with swallowing, abdominal pain, vomiting or diarrhea, cough, fever or difficulty breathing.


In babies, consequences can last a lifetime or be fatal. In healthy people, CMV is almost always mild and goes away on its own. People with weakened immune systems can lose their vision or have life-threatening and disabling illnesses that can require lifelong therapy to prevent these complications.

Additional info

Centers for Disease Control and Prevention (CDC)

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.