Page last reviewed: 13/07/2011

Cytomegalovirus (CMV) is a common virus.

CMV is part of the herpes family of viruses. As with most other herpes-type viruses, once you are infected with CMV, it will remain inactive in your body for the rest of your life. CMV causes few symptoms in most people.

CMV is spread through bodily fluids, such as saliva and urine. It can be passed on through close bodily contact. For example, the infection can be found in small droplets of saliva which are spread from one person to another when an infected person coughs or sneezes.

There is no cure for CMV. Possible vaccines for the condition are currently being researched and used in clinical trials, but a vaccine will probably not become publicly available for several years.

How common is CMV?

CMV is one of the most common viral infections. It is estimated that around half of all adults in Ireland have been infected by CMV. Most people develop the infection during early childhood or as a teenager.

Types of CMV

The different types of CMV infection are:

  • primary CMV - where someone develops a CMV infection for the first time
  • reoccurring CMV - a previously inactive CMV infection is reactivated, often because the immune system (the body's natural defence against infection and illness) is weakened
  • re-infection with CMV - an infection with a different strain of virus
  • congenital CMV - a CMV infection develops when a woman is pregnant and infects the unborn baby


Unlike many viral infections, CMV causes few if any symptoms. Most people do not know they have developed an infection.

CMV is only serious when it develops or reoccurs in certain vulnerable groups of people. The two main groups of people at risk from CMV are:

  • people with a weakened immune system, particularly those with HIV or who have recently had an organ transplant or a bone marrow transplant
  • unborn babies


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 people.

These types of infections have become much less common since the introduction of more effective anti-HIV medicines during the 1990s.

Organ transplants

To prevent their body rejecting a donated organ, people who have had an organ transplant take medicines to suppress their immune system (immunosuppressants).

A CMV infection can reoccur as a result of a person's weakened immune system. CMV may also be acquired from the donated organ. If it is not treated, this can lead to organ damage.

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

Unborn babies

If a woman becomes infected with CMV for the first time during pregnancy, there is a risk that she may pass the infection on to her unborn baby. Infection in the unborn baby is known as congenital CMV. It is estimated that 1 to 4 babies in every 200 will be born with congenital CMV.

Only 1 in 10 babies who are born with congenital CMV have symptoms at birth. However, these symptoms can be serious and include long-term problems, such as learning difficulties and hearing loss. A few babies who are born with congenital CMV but have no symptoms at birth will experience hearing loss that develops over their first few years of life. 

Congenital CMV infection is a notifiable disease in Ireland.  Further information on CMV is available on the website of the Health Protection Surveillance Centre at

Page last reviewed: 13/07/2011

The symptoms of cytomegalovirus (CMV) differ depending on whether you have:

  • primary CMV - where someone develops a CMV infection for the first time
  • re-infection with CMV - an infection with a different strain of virus
  • reoccurring CMV - a previously inactive CMV infection is reactivated, often because the immune system (the body's natural defence against infection and illness) is weakened
  • congenital CMV - a CMV infection develops when a woman is pregnant and infects the unborn baby 

Primary CMV

Most cases of primary CMV cause no noticeable symptoms. If you do experience symptoms, they will be similar to flu symptoms and can include:

  • a high temperature of 38C (100.4F) or above
  • extreme tiredness
  • sore throat
  • swollen glands
  • muscle and joint pain
  • loss of appetite

These symptoms should only last for a couple of weeks.

Re-infection with CMV

If you are re-infected with a different strain of the CMV virus, you may not have any symptoms, or you may have symptoms that are similar to a primary CMV infection (see above).

Reoccurring CMV

If CMV reoccurs in healthy people, including during pregnancy, it will cause few if any symptoms.

A CMV infection that reoccurs due to a weakened immune system can cause a wide range of symptoms. This is because the virus can quickly spread throughout the body, causing damage to one or more of your organs. In particular, damage can be done to the digestive system, lungs and eyes.

Symptoms of reoccurring CMV include:

  • a high temperature of 38C (100.4F) or above
  • diarrhoea
  • shortness of breath
  • large painful ulcers in your mouth and oesophagus (gullet)
  • visual disturbances, such as blind spots, blurring and floaters (a black spot or "web" that appears to be floating in your field of vision)
  • pneumonia - inflammation (swelling) of the tissue in your lungs
  • retinitis - inflammation of the retina, the light-sensitive tissue that lines the back of your eyes
  • hepatitis - inflammation of the liver

If you have had a transplant, particularly a bone marrow transplant, a CMV infection can cause a fall in the number of lymphocytes in your body. Lymphocytes are infection-fighting white blood cells that mostly fight viral infections. If you have low levels of lymphocytes, you may be at increased risk of a more serious CMV infection.

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

Congenital CMV

Around 9 out of 10 babies born with congenital CMV experience no symptoms at birth. This is known as an asymptomatic congenital CMV infection.

Hearing loss

A small number of babies with asymptomatic congenital CMV may develop some degree of hearing loss over their first few years of life. Loss of hearing can range from mild to total.

The hearing problems can affect just one ear (unilateral hearing loss) or can cause problems in both ears (bilateral hearing loss). Children with bilateral hearing loss are likely to experience difficulties with speech and communication as they get older.

Symptoms at birth

One in 10 babies born with congenital CMV have symptoms at birth, including:

  • jaundice - yellow-coloured skin and yellowing of the whites of the eyes
  • pneumonia
  • a rash of small, purplish spots
  • an enlarged liver and spleen
  • low birth weight
  • seizures (fits)

While some of these symptoms can be treated, some babies will develop long-term conditions as a result of the infection. Up to 9 out of 10 babies born with congenital CMV who have symptoms at birth will develop one or more physical or mental disabilities. These include:

  • hearing loss
  • visual impairment 
  • blindness
  • learning difficulties
  • lack of physical co-ordination 
  • epilepsy - a condition that affects the brain and causes repeated seizures

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.

Lymph glands
Lymph nodes are small oval tissues that remove unwanted bacteria and particles from the body. They are part of the immune system.

The spleen is an organ that is located behind the stomach and which plays an important role in filtering out harmful bacteria and viruses from the blood.

Page last reviewed: 13/07/2011

Cytomegalovirus (CMV) is a common virus that is part of the herpes family of viruses. 

How CMV is spread

CMV is spread through bodily fluids. These include:

  • saliva
  • semen
  • blood
  • urine
  • vaginal fluids
  • breast milk

Close physical contact

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

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

Most CMV infections occur in early childhood. The infection can spread rapidly in places where young children spend a lot of time in close contact with each other, such as day care centres and nurseries. However, by the time a child is old enough to attend, their immune system (the body's natural defence against infection and illness) should be strong enough to deal with an infection.

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

Reoccurring CMV

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:

  • take immunosuppressant medication after having an organ transplant
  • have HIV
  • are having chemotherapy
  • have been taking oral steroid tablets for more than three months

CMV and breastfeeding

CMV can be passed from a mother to her child through breast milk. However, the benefits of breastfeeding your baby far outweigh any risk from CMV.

The one exception is if a child is born prematurely. The immune system of premature babies is often not strong enough to deal with a CMV infection. If your baby is born prematurely, your treatment team will advise you about the best way to feed your baby.

Congenital CMV

Congenital CMV is when an unborn baby develops a CMV infection from its mother.

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 about 4 out of 10 cases, the baby will be infected as well.

In some cases, a previously inactive CMV infection can reoccur during pregnancy as a result of the mother having a weakened immune system. The mother could also be re-infected with another strain of the CMV virus. If this happens, the CMV virus can be passed from the mother to her unborn baby.

In most cases where CMV is passed from a mother to her unborn baby, the virus does not cause any damage to the baby. However, if a large amount of the virus is spread to the baby, it can interfere with the baby's normal development, resulting in symptoms and associated disabilities of congenital CMV.

Page last reviewed: 13/07/2011

If you think you have developed a cytomegalovirus (CMV) infection for the first time, you do not need to see your GP for a diagnosis as long as you are otherwise healthy.

Blood test

A blood test will be carried out if it is necessary to diagnose CMV, for example because you are going to have an organ transplant.

Regular testing for CMV may be recommended if you:

  • have a condition that weakens the immune system, such as HIV 
  • are receiving a treatment that is known to weaken the immune system, such as chemotherapy

If you have a CMV infection, your immune system (the body's natural defence against infection and illness) will produce special cells called antibodies to fight off the infection. The blood test will check whether or not antibodies are present in your blood.

Congenital CMV

If it is thought that your newborn baby may have congenital CMV, the virus can usually be detected by examining a sample of their body fluids, such as their urine or blood.

Page last reviewed: 13/07/2011

Primary CMV

If you have symptoms after being infected with cytomegalovirus (CMV) for the first time, painkillers that are available from pharmacies, such as paracetamol or ibuprofen, can help relieve the symptoms of fever and pain. Children under 16 years of age should not take aspirin.

Drinking plenty of water or unsweetened fruit juice will help relieve the symptoms of fever and sore throat, as well as preventing dehydration.

Congenital and reoccurring CMV

Congenital CMV and CMV that reoccurs due to a weakened immune system (the body's natural defence against infection and illness) can be treated with antiviral medicines. Antiviral medicines cannot cure a congenital CMV infection, but can slow its progress.

Antiviral medicines

Ganciclovir (brand name Cymevene) is an antiviral medicine that is often used to treat CMV. However, it cannot usually be given during pregnancy.

Ganciclovir can cause several side effects. One of the main side effects is bone marrow suppression. Bone marrow is a spongy material found in the hollow centres of some bones. It contains special cells called stem cells, which produce other specialised cells such as:

  • red blood cells, which carry oxygen around the body 
  • white blood cells, which help fight infection
  • platelets, which help stop bleeding

If ganciclovir suppresses your bone marrow, these specialised cells may not be produced. This can lead to a low white blood cell count and, therefore, an increased risk of a serious bacterial infection. Low levels of platelets can cause increased bleeding, and a lack of red blood cells can cause anaemia, which may lead to extreme tiredness.

Other possible antiviral medicines include: 

  • valaciclovir - this may be used after a kidney transplant to prevent infection
  • valganciclovir (brand name Valcyte) 
  • foscarnet (brand name Foscavir)
  • cidofovir (brand name Vistide)

These medicines can also cause side effects. The links above provide more information about them.

Hospital treatment

It may be necessary to keep babies who are born with congenital CMV in hospital until their normal organ function, such as their liver function, returns. They will also need to stay in hospital if they are being treated with the antiviral medicine ganciclovir.

Adults with a weakened immune system and who have organ damage as a result of CMV may require hospital admission.

Page last reviewed: 13/07/2011

If you are pregnant, you can take steps to avoid getting a cytomegalovirus (CMV) infection. People at increased risk of developing CMV, such as people receiving an organ transplant or having chemotherapy (a treatment for cancer), can also take steps to avoid getting an infection.

Pregnant women

If you are pregnant, taking some basic precautions can reduce your risk of developing a CMV infection:

  • Wash your hands regularly using soap and hot water, particularly before preparing food, before eating, after close contact with children and after changing nappies.
  • Avoid kissing a young child on the face. Hugging a child, or kissing them on the head, presents no extra risk.
  • Do not 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 day care centre or nursery.

If your job involves spending a considerable amount of time with young children, you can have a blood test to find out whether you have previously been infected with CMV.

Organ transplants

CMV is one of the main causes of illness and death during the first six months after having an organ transplant. Up to half of people who receive a transplant will develop a CMV infection that causes symptoms.

If you are having an organ transplant, you may be given antiviral medicines to help prevent a CMV infection developing. For example, you may be given antiviral medication if you are having a:

  • kidney transplant 
  • heart transplant 
  • liver transplant 
  • lung transplant 
  • pancreas transplant 

If you have previously been infected with the CMV virus, or if you are receiving an organ from a donor who has previously been infected, you may need to take one of the following antiviral medicines:

  • aciclovir 
  • ganciclovir (brand name Cymevene)
  • valganciclovir (brand name Valcyte) 
  • valaciclovir 

These medicines can reduce the risk of a CMV infection causing symptoms by around 60%, and they can reduce the risk of death by around 40%.


Chemotherapy lowers the amount of infection-fighting white blood cells in your body. If the number of white blood cells is reduced, your immune system (the body's natural defence system against infection and illness) will be weakened and you will be more vulnerable to infections, including CMV.

As well as maintaining a high level of hygiene (see the box, right), you can help prevent infections developing by:

  • having daily showers or baths and washing your clothes, towels and bed linen regularly 
  • avoiding contact with people who have serious infections, such as chickenpox or flu
  • taking extra care not to cut or graze your skin - if you do, clean the area thoroughly with warm water, dry it and cover it with a sterile dressing
  • eating a healthy diet that includes lots of fresh fruit and vegetables
  • resting when you need to

Contact your GP if you think you may have an infection, for example if you have a high temperature of 38C (100.4F) or above or you are feeling shivery.


Possible vaccinations for CMV are being researched. 

One possible vaccine is aimed at young women. The theory is that vaccinating women before they become pregnant could reduce the risk of congenital CMV.

Another possible vaccine is aimed at people who are having organ transplants. The aim is to prevent the donated organ causing a new CMV infection or reactivating an existing CMV infection.

Due to the stringent safety checks that all new medicines and vaccinations have to go through, it will be several years before routine vaccinations against CMV become available.

Good hygiene

Maintaining high levels of hygiene may help prevent a cytomegalovirus (CMV) infection developing. For example, always wash your hands:

  • before preparing, serving or eating food
  • after going to the toilet
  • after changing a baby’s nappy
  • after you have touched any body fluids, such as semen or urine

Clean any surfaces that have come into contact with any body fluids and wear disposable gloves while doing this.

Content provided by NHS Choices and adapted for Ireland by the Health A-Z.

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