Cytomegalovirus, also known as CMV, is a virus. Most humans are exposed to this virus in their lifetime, but typically only individuals with weakened immune systems become ill from CMV infection.

The majority of adults have antibodies (an indication of previous infection) to it in their blood by age 40. Usually CMV produces no symptoms. However, serious CMV infections can occur in people with impaired immunity (immunocompromised host), such as those with AIDS, organ transplant and bone marrow transplant recipients, and people receiving chemotherapy or other immunosuppressive treatments.

Infections can include: CMV pneumonia, CMV gastroenteritis, CMV retinitis, and CMV encephalitis, and a mononucleosis-like illness.

Once a person becomes infected, the virus remains alive, but usually dormant, within that person's body for life. Rarely does it cause recurrent disease, unless the person's immune system is suppressed due to therapeutic drugs or disease. Therefore, for the vast majority of people, CMV infection is not a serious problem.

Primary CMV infection in pregnant women can cause harm to the developing fetus. The CDC recommends that women who are pregnant and have never been exposed to CMV should follow the precautions listed below.

• Throughout the pregnancy, practice good personal hygiene. Hand washing with soap and water, especially after contact with diapers or oral secretions (particularly of a child who is in day care), is very important.
• Women who develop a mononucleosis-like illness during pregnancy should be evaluated for CMV infection and counseled about the possible risks to the unborn child.
• Laboratory testing for antibody to CMV can be performed to determine if a woman has already had CMV infection.

The symptoms of CMV infection are similar to those of mononucleosis. In fact, in 8% of individuals with mononucleosis CMV is the cause. The symptoms of primary CMV infection are listed below.

• prolonged fever
• general discomfort, uneasiness, or ill feeling (malaise)
• loss of appetite
• fatigue
• night sweats
• muscle aches or joint pain
• joint stiffness
• weakness
• weight loss

In an immunocompromised individual, CMV can attack specific organs. The major symptoms of these organ-specific infections are listed below.

Eye:

• Visual impairment
• Blindness

Lung:

• Pneumonia with impaired oxygen uptake (hypoxia)

Gastrointestinal:

• diarrhea
• ulcerations with bleeding

Brain:

• Encephalitis with behavioral changes
• seizures
• coma

• Blood or urine culture: a blood or urine test that attempts to grow the virus in the laboratory. It can take up to 3 weeks to obtain the result of this test.
• CMV PCR: a blood test that detects the presence of and amount of CMV in the blood.
• CMV antigenemia: a blood test that detects the viral particles on the surface of white blood cells. This can tell you if the virus is actively replicating in the body or simply present in a dormant state.
• CMV serology: a test to detect antibodies in the blood targeted against CMV. These antibodies can be of two types: IgG (old infection) or IgM (new infection). Typically, patients have both of these types of antibodies.
• Tissue biopsy for culture: a biopsy of the tissue (often times lung or stomach) thought to be infected with CMV is cultured in the laboratory. The tissue can then be examined for evidence of viral infection and presence of CMV viral particles.

The objective of treatment is to stop the replication of the virus within the body through the use of antiviral agents. These drugs DO NOT eliminate the virus from the body -- they only keep it from dividing.

The most commonly used drugs are ganciclovir, valganciclovir, foscarnet, and cidofovir. These are used in patients in whom CMV disease is established throughout the body.

For CMV infection of the eye, the drug valgancyclovir has been shown to suppress progression of CMV retinitis in HIV patients. A new drug named Fomivirsen has recently been approved by the FDA, and works via direct injection into the eye.

Foscarnet and cidofovir are associated with significant nephrotoxicity (kidney damage) and electrolyte abnormalities, which may require supplementation by intravenous electrolytes. Ganciclovir can cause neutropenia (severe depletion of white blood cells).

There is evidence that resistance to some of these drugs exists, especially to ganciclovir. Newer medications to fight CMV are in development.

CMV infection in the immunocompromised host can be life-threatening, and the severity of the disease is dependent on the strength of the individual's immune system. Individuals who have undergone bone marrow transplant have been shown to have the highest mortality risk.

Any immunocompromised person, whether an HIV patient, organ transplant recipient, bone marrow transplant recipient, or medically immunosuppressed individual, should seek out medical advice if any signs of infection should occur.

• low white blood cell count with use of ganciclovir
• kidney impairment with use of foscarnet
• pneumonia
• meningitis
• blindness

The mechanism of transmission of CMV from one person to another is unclear, but studies suggest it is transferred via bodily fluids. It also appears that children are a significant vector for transmission.

Studies have shown that the use of foscarnet and ganciclovir in individuals who have received bone marrow or solid-tissue transplants can help prevent the development of CMV disease.

Frequently Asked Questions (FAQ):

Who should be tested for CMV? Anyone who has symptoms of infectious mononucleosis, but has negative test results for mononucleosis and Epstein Barr virus. Anyone who shows signs of hepatitis, but has negative test results for Hepatitis A, B, and C.

Should I get my children tested for CMV? There is no need to either screen for CMV or exclude CMV-excreting children from schools or institutions because the virus is frequently found in many healthy children and adults.