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Cytomegalovirus

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.

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

CMV spreads very easily. Infected people may shed the virus in their urine or saliva for months. The virus is also excreted in cervical mucus, semen, stool, and breast milk. Thus, the virus is spread through sexual and nonsexual contact. CMV infection may develop in people who receive a transfusion of infected blood or an infected organ transplant.

CMV may cause symptoms soon after infection. It can remain dormant in various tissues for life. Various stimuli can reactivate the dormant CMV, resulting in disease.

Symptoms

The vast majority of people infected with CMV have no symptoms. A few infected people feel ill and have a fever. CMV infection in adolescents and young adults can cause an illness with symptoms of fever and fatigue that resembles infectious mononucleosis. If a person receives a transfusion of blood containing CMV, fever and sometimes liver inflammation may develop 2 to 4 weeks later.

If a person with a severely weakened immune system becomes infected with CMV, the infection may be severe, sometimes resulting in serious disease or death. In people with AIDS, CMV infection is a common viral complication. The virus tends to 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, miscarriage, stillbirth, or death of the newborn may result. Death is caused by bleeding, anemia, or extensive damage to the liver or brain. Newborns who survive may have hearing loss and mental retardation.

Diagnosis and Treatment

CMV infection may develop gradually and not be recognized immediately. Diagnosis is often unnecessary in healthy adults and children because treatment is unnecessary. However, doctors always consider the possibility of CMV infection in people who have a weakened immune system and an eye, a brain, or a gastrointestinal infection. CMV infection is also suspected in newborns who have a fever or 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 culturing the urine. In people with a weakened immune system, doctors may be able to identify the virus in a sample of blood, other body fluids, or lung or other tissues. Blood tests to estimate how many viruses are present may be done. CMV retinitis can be identified by an ophthalmologist, who examines internal eye structures to check for characteristic abnormalities using an ophthalmoscope.

Mild CMV infection is usually not treated. It subsides on its own. When the infection threatens life or eyesight, an antiviral drug may be given. For people with CMV retinitis, a small device containing sustained-release ganciclovir can be implanted in the eye. Occasionally, ganciclovir or foscarnet is injected directly into the eye. These drugs have serious side effects and may not cure the infection. However, treatment slows the disease's progression and preserves sight. If CMV infection occurs in people whose immune system is temporarily weakened or suppressed (by a disorder or drug), the infection usually subsides without treatment when the immune system recovers or the drug is stopped.
People who have had an organ transplant are often given antiviral drugs to prevent CMV infection.




http://www.merck.com/mmhe/sec17/ch198/ch198h.html



 

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