What Is Cytomegalovirus? What Are The Causes Of Cytomegalovirus Infection?

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Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Immune System / Vaccines;  Pregnancy / Obstetrics;  Pediatrics / Children's Health
Article Date: 11 Dec 2009 - 7:00 PDT

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Cytomegalovirus, also known as HCMV, CMV or Human Herpes virus 5 (HHV-5) is part of the herpes family of viruses. It is a common virus and spreads through bodily fluids, including saliva, blood, breast milk, semen and urine. Cytomegalovirus is human-to-human transmissible through close bodily contact (coughs and sneezes are also possible routes).

As is the case with other viruses in the herpes family, when humans are infected it remains dormant in the body for the rest of their life when it is not active.

Research is currently underway for a potential CMV vaccine. However, there is no current cure for CMV infection. Medications can help newborns and people with weak immune systems.

CMV is widespread and people of either sex, any age group, and those of all ethnic groups may be infected. As CMV infection symptoms are commonly rare, many people do not know they have it. There may be complications if the patient is pregnant (danger to the developing fetus) or has a weakened immune system.

According to the CDC (Centers for Disease Control and Prevention), USA, between 50% and 80% of all adults in the USA are infected. The World Health Organization (WHO) estimates that about 40% of all adults worldwide are infected, as indicated by the presence of antibodies in the general population.

CMV is the virus most commonly transmitted to a developing fetus.

According to Medilexicon's medical dictionary

Cytomegalovirus is "A group of viruses in the family Herpesviridae infecting humans and other animals, many of these viruses having special affinity for salivary glands, and causing enlargement of cells of various organs and development of characteristic inclusions (owl eye) in the cytoplasm or nucleus. Infection of embryo in utero may result in malformation and fetal death. They are all species specific and include salivary virus, inclusion body rhinitis virus of pigs, and others."

The word "Cytomegalovirus" comes from the Greek word cyto meaning "cell", and the Greek word megalo meaning "large".

There are three main types of CMV infections:

• Acquired CMV, or primary CMV - a first-time infection.


• Recurring CMV - the patient is already infected, the virus is dormant and then becomes active due to a weak immune system.


• Congenital CMV - CMV infection occurs during pregnancy and affects the fetus (unborn baby).

CMV is not a concern for most of the general population. It is only a problem when it affects certain groups of people, including:

• Patients with weakened immune systems - such as those who have recently received a transplant, and people with HIV.
  
  
  • Advanced HIV patients whose immune systems have been seriously undermined are much more likely to experience CMV infection recurrence, which can result in organ failure, including eye damage and blindness. The problem is smaller now than it used to be during the 1980s, thanks to better anti-HIV medications.
  
  
  • Organ and bone marrow transplant recipients have to take immunosuppressants - drugs which lower their immune systems so that their bodies do not reject the new organs (or bone marrow). The dormant CMV is much more likely to become active in these patients. CMV infection can lead to organ damage. Organ transplant recipients are often given anti-viral medicines as a precaution against CMV.


• Pregnancy and congenital CMV
  
  
  • The danger is to the developing fetus (unborn baby), rather than the mother. If an uninfected woman becomes infected with CMV during her pregnancy there is a significant risk that the developing fetus will become infected. The National Health Service (NHS), UK, estimates that approximately 0.5% of all babies born have congenital CMV; The Mayo Clinic, USA, estimates 1%.
    
    Of the infected babies, only about 10% will have symptoms when they are born. However, the symptoms may be severe and can result in long-term complications, including learning difficulties. Another 10% of babies born infected will have no symptoms, but will eventually have hearing problems.

What are the signs and symptoms of CMV?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

Signs and symptoms of CMV depend on several factors:

• Is it Acquired CMV?
  
  In the vast majority of cases there will be no noticeable symptoms. When signs and symptoms do occur, they may include:
  
  
  • An elevated body temperature (fever), often prolonged
  • Night sweats
  • Tiredness, general feeling of illness, uneasiness
  • Sore throat
  • Swollen glands
  • Joint pain
  • Muscle pain
  • Lack of appetite
  • Weight loss
  
  Symptoms will generally go away after two weeks.


• Has a dormant CMV become active due to a weakened immune system (recurring CMV)?
  
  Symptoms of recurring CMV vary, depending which organs are affected. The most likely affected areas are the eyes, lungs or digestive system. Recurring CMV signs and symptoms may include:
  
  
  • An elevated body temperature (fever)
  
  
  • Diarrhea, gastrointestinal ulcerations, and gastrointestinal bleeding
  
  
  • Panting (shortness of breath)
  
  
  • Pneumonia with hypoxemia (low blood oxygen)
  
  
  • Ulcers in the mouth; sometimes they can be fairly large and unpleasant
  
  
  • Problems with vision, including floaters, blind spots and possibly blurred vision. In some cases symptoms may be more severe.
  
  
  • Hepatitis (inflamed liver), often characterized by prolonged fever
  
  
  • Encephalitis (brain inflammation), which may include behavioral changes, seizures, and even coma.
  
  Any patient with a weakened immune system who experiences any of these symptoms should tell their doctor straight away.


• Is it Congenital CMV (was the baby born infected)?
  
  Hearing loss - approximately 90% of babies who are born infected with CMV have no signs or symptoms. 10% of the 90% will eventually develop healing loss; in the majority of cases during their first six months of life. Levels of deafness may vary from slight to total. Half of these children will have unilateral hearing loss (just one ear), while the other half will have bilateral hearing loss (both ears). Children with bilateral hearing loss are much more likely to have speech and communication problems later on.
  
  If there are symptoms of Congenital CMV (at birth), they may include:
  
  
  • Jaundice - the skin and sclerae (whites of the eyes) take on a yellowish color.
  • Pneumonia
  • Red spots under the skin
  • Purple skin splotches or a rash (possibly both)
  • Enlarged liver
  • Enlarged spine
  • Below-normal birth weight
  • Seizures - uncontrolled electrical activity in the brain, which may cause a physical convulsion.
  
  Some of these symptoms are treatable. However, according to the National Health Service (UK), between 85% and 90% of babies born with congenital CMV will have one or more of these disabilities during their lives:
  
  
  • Autism
  • Central vision loss, scarring of the retina, uveitis (swelling and irritation of the eye)
  • Cognitive difficulties (including learning difficulties)
  • Deafness (varying degrees)
  • Epilepsy
  • Impaired vision
  • Problems with physical coordination
  • Seizures
  • Small head

What are the causes of Cytomegalovirus infection?

• Acquired (primary) Cytomegalovirus may spread from human-to-human via:
  
  
  • Saliva - includes coughs and sneezes
  • Semen
  • Blood
  • Urine
  • Vaginal fluids
  • Breast milk - the benefits of breastfeeding far outweigh CMV risks. If the baby is born premature the medical team will advise on how the baby should best be fed.
  
  Infection may also occur by touching an infected surface - the surface was infected with saliva or urine, somebody touches it and then touches the inside of their nose or mouth.
  
  Most humans become infected during childhood; daycare centers, nurseries, and places where children are in close contact with each other are common environments. Parents should not be put off sending their children to daycare or nurseries - by the time they are old enough to go to these places their immune systems are able to deal with an infection.


• Recurring CMV - the following patients may have a weakened immune system which makes them more susceptible to recurring CMV:
  
  
  • Organ transplant recipients who are taking immunosuppressant medication
  • Patients with HIV
  • Patients receiving chemotherapy
  • Patients who have been taking oral steroid for over three months


• Congenital CMV - most cases occur when the woman is infected with CMV for the first time, either during her pregnancy or shortly before it starts.
  
  In some rare cases the mother may have a previously dormant CMV infection, which recurs during pregnancy. The mother most likely has a weakened immune system. In such cases the virus may be transmitted to the developing embryo/fetus.

Diagnosing CMV

Blood test - a blood test can detect antibodies (special proteins in the blood) which are created when the immune system responds to the presence of CMV. Cultures or a PCR (polymerase chain reaction) test from blood, body fluids, or a tissue biopsy can detect the presence of the virus.

Diagnosing a baby - a pregnant woman has a very small risk of reactivation infecting her developing baby.

• Amniocentesis - if a new infection is detected during her pregnancy, the mother may consider amniocentesis. The doctor extracts a sample of amniotic fluid to determine whether the virus is present. This test may be recommended if the doctor detected something during an ultrasound scan of the baby.


• Early testing of the baby - if Congenital CMV is suspected the baby must be tested within the first three weeks of his/her life. Tests carried out later will not be conclusive for congenital CMV, because the baby may have become infected after birth.

People with weakened immune systems - any patient that has a weakened immune system should be tested, even if there is no active CMV infection. Anybody who is immunocompromised should undergo regular monitoring for CMV complications; including vision and hearing problems.

What are the treatment options for CMV?

• Treatment for acquired CMV - patients infected for the first time who experience symptoms may find that OTC (over-the-counter, no prescription required) painkilling medications, such as Tylenol (paracetamol), ibuprofen or aspirin (patient must be over 16 years of age for aspirin) will help relieve symptoms.
  
  The patient should take plenty of fluids while there are symptoms.


• Treatment for congenital and reoccurring CMV - anti-viral medications cannot cure CMV infection, but they can slow down the rate at which it spreads. An example is ganciclovir; possible side-effects may include:
  
  
  • An elevated body temperature (fever)
  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Hallucinations
  • Confusion
  • Seizures
  
  Newborns may need to stay in hospital until their organ functions return to normal. Adults with weakened immune systems may also have to be hospitalized if there is extensive organ damage.

What are the possible complications of CMV?

Healthy people very rarely become sick from CMV infection. If they do occur, they may include:

• CMV mononucleosis - excess of mononuclear leukocytes (monocytes) in the blood - in other words, too many white blood cells that have a single nucleus. Symptoms include sore throat, swollen glands, swollen tonsils, tiredness and nausea. It can cause liver inflammation (hepatitis) and spleen enlargement.


• Gastrointestinal problems - including diarrhea, fever, abdominal pain, colon inflammation, and blood in feces (stools).


• CNS (central nervous system) complications - for example, encephalitis (inflammation of the brain).


• Pneumonitis - inflammation of lung tissue.

Prevention of CMV infection

The following precautions may help lower the risk of contracting CMV; they are especially applicable for pregnant women:

• Hand washing - wash your hands regularly with soap and water.


• Kissing a young child - avoid tear and saliva contact. Some experts say kissing should be done on the forehead rather than on the lips.


• Sharing kitchen utensils - avoid sharing glasses and kitchen utensils, i.e. do not pass your glass around, or pick up another person's drink to have a sip.


• Disposable items - such as diapers, paper-handkerchiefs (tissues), etc. should be discarded and dealt with carefully. Do not touch your face with your hands after disposing them or touching them before washing them thoroughly.


• Condom - during sex wear a condom to prevent the spread of CMV via vaginal fluids and semen.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today