Cytomegalovirus 

Types of CMV

The three main types of CMV infections are:

* Acquired (or primary) CMV: a CMV infection that is contracted for the first time;
* Reoccurring CMV: a previously dormant CMV infection that reoccurs due to a weakened immune system;
* Congenital CMV: a CMV infection that develops in pregnancy and can affect the unborn baby;

HIV
People with advanced HIV, who have a severely weakened immune system, can sometimes experience a reoccurrence of a CMV infection, which can lead to organ failure. Eye damage which can cause blindness often occurs in these cases.

These types of infections were widespread in the 1980s, but are much less common now due to the more effective anti-HIV medicines introduced during the 1990s.

Organ transplants
In order to prevent their body rejecting a donated organ, people who have recently undergone an organ transplant often have to take medicines that suppress their immune system (immunosuppressants).

In many cases, a previously dormant CMV infection can reoccur as a result of a person’s weakened immune system, and can lead to organ damage.

Anti-viral medicines are often given to people who have had an organ transplant as a precaution against CMV.

Unborn babies
If a woman who was previously uninfected by CMV becomes infected during pregnancy, there's a risk that she may pass the infection on to her unborn baby. This is known as a congenital CMV. It is estimated that one in every 200 babies will be born with congenital CMV.

Only 10% of babies who are born with congenital CMV will have symptoms at birth. But these symptoms can be serious and may lead to long-term complications such as learning difficulties.

A further 10% of babies who are born with congenital CMV will have no symptoms at birth, but will experience hearing loss in later life.

See Prevention, above, for more information about how to prevent a CMV infection during your pregnancy.

Symptoms of cytomegalovirus 

The symptoms of cytomegalovirus (CMV) differ depending on:
* whether you have contracted a CMV infection for the first time (an acquired or primary CMV infection);
* whether a previously dormant CMV infection has reoccurred because you have a weakened immune system, or;
* whether the CMV infection has developed in a newborn baby (congenital CMV);

Symptoms of acquired CMV
In 90% of cases of acquired CMV there will be no noticeable symptoms. If you do experience symptoms, they will be similar to flu symptoms and include:

* fever (a temperature of 38°C (100.4°F) or above) ;
* fatigue;
* sore throat;
* swollen glands;
* muscle and joint pain, and;
* loss of appetite ;

These symptoms should only last for a couple of weeks.

Symptoms of reoccurring CMV
The symptoms of a CMV infection that reoccurs as a result of a weakened immune system are wide ranging. This is because the virus can quickly replicate and spread throughout the body, causing damage to one or more of your organs, in particular, the digestive system, lungs and eyes.

Possible symptoms of reoccurring CMV include:

* fever (a temperature of 38°C (100.4°F) or above);
* diarrhoea;
* shortness of breath;
* large painful ulcers in your mouth, and;
* visual disturbances such as blind spots, blurring and floaters (a black spot or ‘web’ that appears to be floating in your field of vision);

If you have a weakened immune system and experience one or more, of these symptoms, immediately contact your treatment team and/or your GP.

Symptoms of congenital CMV
Hearing loss
Around 90% of babies born with congenital CMV will experience no symptoms at birth. However, of these, one in 10 will develop varying degrees of hearing loss, usually during the first six months after birth. The level of hearing loss can range from mild to total.

Around half the children who develop hearing problems will only have problems in one ear, and half will have problems in both ears (bilateral hearing loss). Children with bilateral hearing loss are likely to experience speech and communication difficulties as they grow older.

See Useful links for more information about hearing loss.

Symptoms at birth
Symptoms of CMV that develop at birth include:

*jaundice: yellow coloured skin and yellowing of the whites of the eyes ;
* pneumonia (lung infection);
*red spots under the skin ;
*enlarged liver and spine ;
* low birth weight, and;
* seizures;

While some of these symptoms can be treated, 85 to 90% of babies who are born with congenital CMV will have one or more physical and/or mental disabilities.

These include:

* hearing loss;
* impaired vision;
*blindness ;
*seizures ;
*learning difficulties ;
* lack of physical coordination;
* autism, and;
* epilepsy;

Causes of cytomegalovirus 

Acquired cytomegalovirus
The cytomegalovirus (CMV) is spread through bodily fluids. These include:

* saliva;
* semen;
* blood;
* urine;
* vaginal fluids, and;
* breast milk;

Close physical contact
CMV infection can be spread through close physical contact. For example, when small droplets of infected saliva are transmitted from one person to another when an infected person coughs or sneezes.

You can also contract the CMV virus by touching surfaces that have been infected with contaminated saliva or urine, and then touching the inside of your mouth or nose. CMV can also be spread during sexual intercourse.

Most CMV infections occur in early childhood. In places where young children spend a lot of time in close contact with other children, such as daycare centres and nurseries, a rapid spread of a CMV infection can occur.

However, do not avoid sending your child to daycare or nursery because by the time they're old enough to attend, their immune system should be strong enough to deal with an infection.

If you do experience any symptoms of a CMV infection, they should pass quickly and the virus will then lie dormant in your body’s cells for the rest of your life.

CMV will only become a problem if your immune system becomes severely weakened, leading to the virus ‘waking up’ and re-infecting your body’s organs.

Your immune system may become weakened if:

*you're taking immunosuppressant medication because you've had an organ transplant ;
* you have HIV;
* you are receiving chemotherapy;
* you have been taking steroid tablets (oral steroids) for more than three months;

CMV and breastfeeding
CMV can be passed from a mother to a child through breast milk. However, the benefits of breastfeeding your child far outweigh any risk that is posed by CMV.

The one exception to this is if a child is born prematurely. The immune systems of premature babies are often not strong enough to control a CMV infection. If your baby is born prematurely, your treatment team will be able to advise you about the best option for feeding your baby.

Congenital CMV
Most cases of congenital CMV develop when a pregnant woman is infected by the CMV virus for the first time during (or shortly before) pregnancy.

In some cases, a previously dormant CMV infection can recur during pregnancy as a result of the mother having a weakened immune system. If this happens, the CMV virus can then be transmitted from the mother to the unborn baby.

In the majority of cases where CMV is transmitted from a mother to her unborn baby, the virus doesn't cause any damage to the baby. But if a large number of virus cells (high viral load) is spread to the baby, it can interfere with the baby’s normal development, resulting in the symptoms and associated disabilities of congenital CMV.

Diagnosing cytomegalovirus 

Blood test
Cytomegalovirus (CMV) can be diagnosed by a blood test. If you're infected, or have been previously infected, your immune system will produce special cells, called antibodies, to fight off the infection. The blood test checks whether or not antibodies are present in your blood.

If you have a condition such as HIV, or are receiving a treatment that is known to weaken the immune system, such as chemotherapy, regular testing for CMV may be recommended.

Treating cytomegalovirus 

Acquired CMV
If you experience symptoms after being infected with cytomegalovirus (CMV) for the first time, over-the-counter (OTC) painkillers such as paracetamol or ibuprofen can help relieve the symptoms of fever and pain. Children under 16 should not take aspirin.

It is very important to drink plenty of water or unsweetened fruit juice, as this will help relieve the symptoms of fever and sore throat, and prevent dehydration.

Congenital and reoccurring CMV
Congenital CMV and CMV that recurs due to a weakened immune system can be treated with anti-viral medicines. These medicines can't cure it, but they can slow its spread.

Ganciclovir is an anti-viral medicine that is often used to treat CMV. However, this medicine can cause a range of side-effects including

* fever (a temperature of 38°C (100.4°F) or above);
* nausea;
*vomiting ;
*diarrhoea ;
* abdominal pain;
* headache;
* confusion;
* hallucinations, and;
* seizures;

It may be necessary to keep babies who are born with congenital CMV in hospital until their normal organ function, such as liver function, returns.

Adults with a weakened immune system, who have extensive organ damage as a result of CMV, may also require admission to hospital.

Preventing cytomegalovirus 

Congenital CMV
If you're pregnant, taking some basic precautions can reduce your risk of developing a cytomegalovirus (CMV) infection.

• Wash your hands regularly using soap and hot water, particularly before preparing food, before eating, after close contact with children, or after changing nappies.
  
• Avoid kissing a young child on the face. Hugging a child, or kissing them on the head, presents no extra risk.
  
• Don't share eating utensils (forks and spoons) with young children, or drink from the same glass as them.

These precautions are particularly important if you have a job that brings you into close contact with young children, such as working in a daycare centre or nursery.

If you have a job where you spend a considerable amount of time with young children, consider having a blood test to determine whether you have previously been infected with CMV. If the result of the test reveals that you have not had a CMV infection, you may wish to consider transferring to a role that limits your exposure to young children.

References 

Adler SP, Nigro G, Pereira L (2007). Recent advances in the prevention and treatment of congenital cytomegalovirus infections. Semin Perinatol. 2007 Feb;31(1):10-8

Center for Disease Control (2008). Information about CMV for Clinicians and Others in Healthcare Settings

Fowler KB, Stagno S, Pass RF (2003). Maternal Immunity and Prevention of Congenital Cytomegalovirus Infection. JAMA. 2003;289(8):1008-1011

Hodson EM, Craig JC, Strippoli GFM, Webster AC. (2008). Antiviral medications for preventing cytomegalovirus disease in solid organ transplant recipients. Cochrane Database of Systematic Reviews 2008, Issue 2. Art. No.: CD003774. DOI: 10.1002/14651858.CD003774.pub3

Jeon J et al (2006). Knowledge and Awareness of Congenital Cytomegalovirus Among Women. Infectious Diseases in Obstetrics and Gynecology, 2006, 80383

Joseph SA et al (2005). Risk factors for cytomegalovirus seropositivity in a population of day care educators in Montréal, Canada. Occupational Medicine, 55(7), 564-7

Kenneson A, Cannon MJ. (2007). Review and meta-analysis of the epidemiology of congenital cytomegalovirus (CMV) infection. Reviews in Medical Virology, 17(4), 253-76

Schleiss MR (2006). Acquisition of human cytomegalovirus infection in infants via breast milk: natural immunization or cause for concern? Reviews in Medical Virology, 16(2), 73-82

Snydman DR. (2006). The case for cytomegalovirus prophylaxis in solid organ transplantation. Reviews in Medical Virology, 16(5), 289-95

Strippoli GF, Hodson EM, Jones CJ, Craig JC. (2006). Pre-emptive treatment for cytomegalovirus viraemia to prevent cytomegalovirus disease in solid organ transplant recipients. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD005133. DOI: 10.1002/14651858.CD005133.pub2

World Health Organisation. Management of Opportunistic Infections in HIV.