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Southern Cross Medical Library

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Cytomegalovirus (CMV)

 
Cytomegalovirus (CMV) is a common, and usually mild viral illness.  However, the severity and duration of symptoms can vary considerably depending on the health and age of the infected individual.  And there is a small risk of serious complications for babies if the disease is contracted by pregnant women (congenital CMV).  People with weakened immune systems may also be at significant risk from cytomegalovirus infection.
 
More than half of the population is estimated to have been infected with cytomegalovirus by the time they reach mid-adulthood.  

Transmission

Cytomegalovirus belongs to the herpes virus family, which also includes viruses responsible for chickenpox, glandular fever and cold sores.
 
As with other members of the herpes virus family, cytomegalovirus remains dormant in the body for life. Reactivation of the virus can occur but this is not common and does not usually result in illness.
 
CMV is not considered to be highly contagious. However any person infected with the CMV virus, be it dormant or an active infection, can transmit the virus to another person. The virus can be carried in body fluids such as urine, tears, saliva, blood, semen, cervical secretions and breast milk. 
 
Transmission can occur during any close contact that allows the transfer of infected body fluids. Most commonly the virus is spread in respiratory droplets when coughing or sneezing. It can also be spread through sexual contact, intravenous drug use, direct contact with the wet nappies of infected children, blood transfusions (though blood banks stringently screen donors and test the blood to ensure the virus is not present) and organ transplantation. CMV can also cross the placenta.
 
Children in day care or preschool are a significant risk group, as these settings put children in close contact with one another, and children do not have the personal hygiene practices that would help to prevent transmission of the CMV virus. 

Signs and symptoms

CMV is usually a mild disease but the severity and duration of symptoms can vary considerably depending on the health and age of the infected individual.
 
Most healthy individuals who have a CMV infection will not have symptoms. However, when symptoms are present they are often similar to those of glandular fever. The incubation period of the CMV virus varies but symptoms usually become apparent about three to 12 weeks after exposure to the virus. Duration of symptoms also varies, though on average they last for two to three weeks.
 

Symptoms may include: 

  • Fever
  • Headache
  • Fatigue
  • Muscle aches
  • Enlarged glands
  • Sore throat
  • Enlarged spleen.

Individuals with weakened immune systems, such as people with HIV infection, organ transplant recipients or cancer patients, are the group at greatest risk of serious complications of CMV infection.  These can be life threatening and may include: 

  • Anaemia
  • Fever
  • Hepatitis
  • Pneumonia
  • Retinitis
  • Inflammation of the brain (encephalitis)
  • Inflammation of the large intestine (colitis). 

Congenital CMV

Congenital CMV (where the virus is passed from the mother to the unborn baby before birth) is an important cause of birth defects. It is usually only a risk when the mother develops a CMV infection for the first time during pregnancy. Most babies will not become infected with the virus and, of those that do, only a small percentage will suffer serious complications. Rarely, congenital CMV can cause the baby to be stillborn.
 

Some babies with congenital CMV may be born with obvious problems such as: 

  • Prematurity
  • Low birth weight
  • Jaundice
  • Enlarged liver and spleen
  • Lung problems
  • Inflammation of the retina in the eye (retinitis).
A percentage of these babies, along with some babies who appeared perfectly healthy at birth, may go on to develop complications such as hearing and sight impairments and developmental problems. In some cases these complications may be severe.
 
Babies can also be infected with the CMV virus as they pass down the birth canal during delivery, though this does not usually result in illness. However, babies born prematurely who become infected with the CMV virus during birth are at greater risk of illness and of complications such as pneumonia and hepatitis.

Diagnosis

As signs and symptoms of CMV are not usually severe or specific the infection is rarely diagnosed.  Individuals infected with CMV develop antibodies (special proteins that help fight and destroy foreign bodies such as viruses).  These antibodies are able to be detected in the blood, therefore blood tests can be used to diagnose CMV infection.  It is usual for two blood samples to be taken two weeks apart before an accurate diagnosis is made.  To diagnose active infection, CMV can also be cultured in saliva, urine and tissue samples. 

Treatment

When the CMV infection results in a mild glandular fever-like illness, bed rest is often all that is required.  Paracetamol to treat fever and discomfort may also be beneficial. As CMV is caused by a virus antibiotics will be of no benefit in combating it.
 
In cases of serious CMV infections in people with weakened immune systems, antiviral medications may be administered. These medications, such as ganciclovir and foscarnet, are usually given as an infusion into the blood stream but can also be given in tablet form. The use of these medications to treat congenital CMV infections is still being researched. 

Prevention

Ensuring that hands are washed often with soap and warm water and are thoroughly dried will help prevent the spread of the virus.
 
Pregnant women should take particular care to avoid contact with individuals known to have CMV. Pregnant women who work with infants and children should be particularly vigilant.
 
Other practices that can help to reduce the transmission of the CMV virus include not sharing needles or syringes and engaging in safe sex practices.
 
Vaccines against CMV are being researched but, at present, no vaccine is available.

References

Anderson, K.N., Anderson, L.E. & Glanze, W. D. (eds.) (2006) Mosby’s medical, nursing, & allied health dictionary (6th ed.) St. Louis: Mosby-Year Book, Inc.
KidsHealth (2012) Cytomegalovirus (CMV) Philadelphia: The Nemours Foundation, Inc.
http://kidshealth.org/parent/infections/bacterial_viral/cytomegalovirus.html
The Children’s Hospital at Westmead (2010) Cytomegalovirus (CMV) Sydney: New Children’s Hospital
http://www.chw.edu.au/parents/factsheets/cytomegj.htm
 
Last reviewed - 23 May 2013 
 
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