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Cytomegalovirus (CMV) Infection


Kenneth M. Kaye

, MD, Harvard Medical School

Last full review/revision Apr 2020| Content last modified Apr 2020

Cytomegalovirus infection is a common herpesvirus infection with a wide range of symptoms: from no symptoms to fever and fatigue (resembling infectious mononucleosis) to severe symptoms involving the eyes, brain, or other internal organs.

  • This virus is spread through sexual and nonsexual contact with body secretions.
  • Most people have no symptoms, but some feel ill and have a fever, and people with a weakened immune system can have serious symptoms, including blindness.
  • Cytomegalovirus can cause serious illness in infants who are infected before birth.
  • Doctors may detect the infection by culturing a sample of infected body fluid, such as urine.
  • Often, no treatment is required, but if the infection is severe, antiviral drugs may be used.

Infection with cytomegalovirus (CMV) is very common. CMV is a type of herpesvirus (herpesvirus type 5). Blood tests show that 60 to 90% of adults have had a CMV infection at some time.

CMV may cause symptoms soon after infection. Also, it remains dormant (inactive) in various tissues for life. Various stimuli can reactivate the dormant CMV, resulting in virus growth which can sometimes cause disease. The lungs, gastrointestinal tract, brain, spinal cord, or eyes may be infected.

Usually, CMV infection causes no symptoms. Serious infections typically develop only in infants infected before birth and in people with a weakened immune system—for example, people with AIDS or those who have received an organ transplant. In people with a weakened immune system, disease often results from reactivation of the dormant virus.

Transmission of CMV

Infected people may shed cytomegalovirus in their urine or saliva intermittently. The virus is also excreted in mucus in the cervix (the lower part of the uterus), semen, stool, and breast milk. Thus, the virus is spread through sexual and nonsexual contact.

If a pregnant woman is infected, the fetus may acquire the infection during the pregnancy, or the baby may acquire the infection during delivery.

CMV infection may develop in people who receive a transfusion of infected blood or an infected organ transplant. People who have received an organ transplant are particularly susceptible to CMV infection because they are given drugs that suppress the immune system (immunosuppressants) to prevent rejection of the transplant.

Symptoms of CMV Infection

Most people infected with cytomegalovirus have no symptoms.

A few infected people feel ill and have a fever.

Infection with CMV, like that with Epstein-Barr virus (EBV, a type 4 herpesvirus), can cause a type of infectious mononucleosis in adolescents and young adults. Both CMV and EBV mononucleosis cause fever and fatigue. But EBV also causes a severe sore throat. CMV does not.

An uninfected person who receives a transfusion of blood containing CMV and becomes infected can have a fever, and sometimes liver inflammation develops 2 to 4 weeks later.

In people with a weakened immune system, CMV can cause serious disease or death.

In people with AIDS, CMV infection is a common viral complication. The virus can infect the retina of the eye. This infection (CMV retinitis) can cause blindness. Infection of the brain (encephalitis), pneumonia, or painful ulcers of the intestine or esophagus may also develop.

If a pregnant woman transmits CMV to the fetus, the following may result:

In newborns, CMV infection may cause extensive damage to the liver or brain. Newborns who survive may have hearing loss and intellectual disability.

Diagnosis of CMV Infection

  • In newborns, urine culture
  • Blood tests
  • In people with a weakened immune system, often biopsy

Cytomegalovirus infection may not be recognized immediately. Diagnosis of CMV infection is often unnecessary in healthy adults and children because treatment is unnecessary. However, doctors consider the possibility of CMV infection in the following people:

  • Otherwise healthy people who have fever and fatigue
  • People who have a weakened immune system and an eye, a brain, or a gastrointestinal infection
  • Newborns who seem sick

Once CMV infection is suspected, a doctor conducts tests to detect the virus in body fluids or tissues.

In newborns, the diagnosis is usually made by sending a sample of urine to a laboratory to grow (culture) and identify the virus.

Blood tests that detect antibodies to CMV can confirm a new infection. (Antibodies are produced by the immune system to help defend the body against a particular attacker, such as CMV.) But these tests cannot confirm whether disease is present. For instance, disease can be caused by reactivation of the virus, as in people with a weakened immune system. In these people, a biopsy of affected tissues is often necessary to confirm CMV disease.

Blood tests to estimate how many viruses are present may also be done.

CMV retinitis can be identified by an ophthalmologist, who examines internal eye structures to check for characteristic abnormalities using an ophthalmoscope.

Treatment of CMV Infection

  • For CMV retinitis, antiviral drugs
  • For people with HIV/AIDS, drugs used to treat HIV infections

Mild cytomegalovirus infection is usually not treated. It subsides on its own.

When the infection threatens life or eyesight, an antiviral drug (valganciclovir, ganciclovir, cidofovir, foscarnet, or a combination) may be given. These drugs may be given by mouth or by vein. When CMV retinitis is very severe, the drugs may also be injected directly into the eye. These drugs have serious side effects (see table Some Antiviral Drugs for Herpesvirus Infections) and do not cure the infection. However, treatment slows the disease's progression and may preserve sight.

Antiviral drugs are used to treat other severe symptoms due to CMV but are less reliably effective than when used to treat retinitis.

If CMV infection occurs in people whose immune system is temporarily weakened or suppressed (by a disorder or drug), the infection usually subsides when the immune system recovers or the drug is stopped.

Treating people who have HIV/AIDS with drugs used to control HIV (antiretroviral drugs) helps protect against CMV infection.

People who have had an organ transplant are often given antiviral drugs (such as ganciclovir, valganciclovir, or foscarnet) to prevent CMV infection.

Drugs Mentioned In This Article

Generic Name Select Brand Names
valganciclovir VALCYTE
ganciclovir CYTOVENE
foscarnet FOSCAVIR
cidofovir VISTIDE

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