What is cytomegalovirus?
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Cytomegalovirus (CMV) is a common virus that is part of the herpes family of viruses.
Many people are first infected with CMV as a child and do not even know they have been infected. However, CMV can be caught at any age. Once you have been infected by CMV, the virus stays in your body for the rest of your life, but does not usually cause further problems.
However, CMV can sometimes recur, which can be a problem if you have a weakened immune system, due to chemotherapy for example. If this happens, the virus can affect your organs and cause problems with vision, ulcers, and pneumonia.
CMV can also cause serious problems if a woman has her first CMV infection during pregnancy, as the infection can spread to the unborn baby (known as congenital CMV).
It is estimated that one to two babies in every 200 will be born with congenital CMV in the UK. Of these, only about 10% will have problems, but they can be serious and include things such as hearing loss and learning difficulties.
Read more about the symptoms of CMV.
How does CMV spread?
CMV is spread through bodily fluids, such as saliva and urine. It can be passed on through close contact with young children, such as changing nappies, or can be spread from one person to another when kissing or having sex.
Read more about the causes of CMV infections.
Can CMV be prevented?
It is not always possible to prevent the spread of CMV and most people don't need to worry about being infected, as the infection is usually mild.
You can reduce your chances of developing an infection by practising good hygiene, such as regularly washing your hands with warm water and soap. This is especially important after changing nappies.
If you have a weakened immune system, you can take further steps to reduce your chances of infection, including taking extra care washing yourself, your clothes and your bed linen regularly.
Possible vaccines for the condition are currently being researched, but will probably not become publicly available for several years.
Read more about preventing CMV.
Treating a CMV infection
As CMV causes no symptoms in most people it is not usually diagnosed. If you are at risk of complications, a blood test can determine if you have ever had CMV or if you have recently caught it for the first time. Blood, urine and saliva swab tests can be used to determine if a newborn baby has congenital CMV.
Most CMV infections are not treated. However, if you have mild symptoms, painkillers can help reduce any fever or pain.
CMV that recurs in someone with a weakened immune system is usually treated with antiviral medicines, which slow the spread of the virus. In some cases, it may be necessary to be treated in hospital. Some babies with congenital CMV may also receive antiviral treatment.
Read more about treating CMV.
The symptoms of cytomegalovirus (CMV) depend on the type of infection you have.
The main types of infection are:
- primary CMV – where someone develops a CMV infection for the first time
- CMV re-infection – an infection with a different strain of the virus from the primary infection
- recurring CMV – a previously inactive CMV infection in the body is reactivated
- congenital CMV – a CMV infection that develops when a woman is pregnant and infects the unborn baby
Most cases of primary CMV cause no symptoms. You may not even realise you have the infection.
- a high temperature of 38oC (100.4oF) 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.
If you are re-infected with a different strain of the CMV virus, you may not have any symptoms, or you may have flu-like symptoms similar to a primary CMV infection.
If CMV recurs in someone who is otherwise healthy, including during pregnancy, it will cause few if any symptoms.
A CMV infection that recurs in someone with a weakened immune system can cause a wide range of symptoms. This is because the virus can quickly spread throughout the body, damaging one or more of your organs – particularly the digestive system, lungs and eyes.
Symptoms of recurring CMV include:
- a high temperature of 38oC (100.4oF) or above
- shortness of breath
- 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 a weakened immune system and have one or more of the symptoms above, contact your doctor or treatment team immediately.
Around 9 out of 10 babies born with congenital CMV experience no symptoms at birth. This is known as an asymptomatic congenital CMV infection.
A small number of babies born with asymptomatic congenital CMV may later develop some degree of hearing impairment during their first few years of life. This is usually permanent and can range from mild to total.
The hearing problems can affect either one or both ears. Children with hearing loss in both ears 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
- 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 nine out of 10 babies who have symptoms at birth will develop one or more physical or mental disabilities. These include:
- hearing loss
- visual impairment or blindness
- learning difficulties
- dyspraxia (lack of physical co-ordination)
- epilepsy – a condition that affects the brain and causes repeated seizures
Infection with cytomegalovirus (CMV) is mainly caused by close physical contact.
How CMV is spread
CMV is primarily spread through bodily fluids, including:
- vaginal fluids
- breast milk
You can get the CMV virus by touching surfaces infected with contaminated saliva or urine, and then touching the inside of your nose or mouth.
CMV can also be spread during kissing or sexual intercourse.
Most CMV infections occur in early childhood. The infection can spread rapidly in places where young children spend 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.
CMV can 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:
- have HIV not currently being treated
- 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. Your treatment team will advise you about the best way to feed your baby if it is born prematurely.
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 four out of 10 cases, the baby will be infected as well.
In some cases, a previously inactive CMV infection can recur during pregnancy if the mother has a weakened immune system. The mother could also be re-infected with another strain of the CMV virus which can also be passed to her unborn baby.
In about 90% of cases, the virus does not harm the baby. However, if a large amount of the virus spreads to the baby, it can interfere with the baby’s normal development, resulting in the associated disabilities and symptoms of congenital CMV.
Cytomegalovirus (CMV) infections only usually require treatment if there is a risk of serious complications.
Most CMV infections do not cause any noticeable symptoms, so do not need to be treated.
If you have symptoms after being infected with cytomegalovirus (CMV) for the first time, over-the-counter painkillers, 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 recurring CMV
Congenital CMV and CMV that recurs 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 and limit the possibility of serious damage.
Treatments for hearing impairment may also be needed.
Ganciclovir (brand name [Cymevene]) is an antiviral medicine 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 centre of some bones, it produces the stem cells that produce blood cells and platelets.
Suppressed bone marrow can lead to a low white blood cell count which increases the risk of 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.
Read more about the [side effects of Cymevene].
Other possible antiviral medicines include:
- valganciclovir (brand name [Valcyte])
- foscarnet (brand name [Foscavir])
- cidofovir (brand name [Vistide])
It may be necessary to keep babies born with congenital CMV in hospital until their normal organ function returns. They will also need to stay in hospital if they are being treated with the antiviral medicine ganciclovir, at least when treatment is first started.
Your baby should also have regular hearing and eye tests to check for any problems.
Adults with a weakened immune system and who have organ damage as a result of CMV may require hospital admission.
It is not always possible to prevent a cytomegalovirus (CMV) infection, but you can take some steps to reduce the risk.
Most people do not need to worry about preventing CMV, as it often causes no symptoms. However, you should be more careful it you are at a risk of more serious problems.
Pregnant women, newborn babies, people receiving an organ transplant or people with a weakened immune system are at an increased risk of serious problems.
Maintaining high levels of hygiene is a simple measure that may help prevent a CMV infection spreading. For example, always wash your hands with soap and warm water:
- before preparing, serving or eating food
- after going to the toilet
- after changing a baby’s nappy
- after you have come into contact with any bodily 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.
CMV infections are common in young children. If you are pregnant, you can reduce your risk of infection with some simple steps, such as:
- wash your hands regularly using soap and hot water, particularly if you have been changing nappies, you work in a nursery or day-care centre
- you should not kiss young children on the face – it is better to kiss them on the head or give them a hug
- do not share food or eating utensils 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. In this case, you can have a blood test to find out whether you have previously been infected with CMV.
CMV is usually only dangerous to the baby if the pregnant mother has not previously had the infection at some point in her life.
CMV used to be one of the main causes of illness and death during the first six months after having an organ transplant. However, antiviral medicines have proved very effective in preventing CMV infections in people who have received transplants.
Therefore, it is likely that you will be given antiviral medicines to help prevent a CMV infection developing if you are having an organ transplant.
Weakened immune system
You may have a weakened immune system if you have HIV or are undergoing chemotherapy to treat cancer. Your immune system is the body's natural defence system against infection and illness, if it is weakened, you will be more vulnerable to infections, including CMV.
As well as maintaining a high level of hygiene, 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 doctor if you are have a weakened immune system and you think you may have an infection, for example if you have a high temperature of 38oC (100.4oF) or above.
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 having organ transplants. The aim is to prevent the donated organ causing a new CMV infection or reactivating an existing CMV infection in the person who receives the transplant.
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.