Cytomegaly

What are cytomegaloviruses?

The cytomegalovirus – also known as cytomegalovirus or CMV for short – belongs to the herpes virus family.
The exact name is “human herpesvirus 5”, abbreviated to HHV-5. Cytomegaloviruses are found all over the world and can infect anyone.
The proportion of adults who become infected with the cytomegalovirus at some point in their lives is estimated to be 50 percent or more in Europe.
In Switzerland, that would be at least 4.5 million people affected.
But very few of them know about it.
This is because the viruses usually do not cause any problems and remain inactive for a long time or even forever.
Doctors call this an “asymptomatic infection” – the viruses have infected the body, but there are no symptoms, i.e. no signs of illness.
However, similar to herpes, the viruses can become active again after a latency phase (“reactivation”).
Unfortunately, it is not possible to rely on cytomegaloviruses behaving inconspicuously.
Three groups of people in particular should be aware that CMV can cause serious health problems:

• Patients who have undergone a transplant and whose immune system is suppressed with medication to protect against rejection of the donor organ.
• People with a weakened immune system, for example with cancer, AIDS or a congenital immune deficiency.
• Women during pregnancy.

The pregnant women themselves are less affected – most women who become infected with cytomegalovirus during pregnancy are not aware of it. However, their babies can be at risk. If they are infected in the womb, they are born with a so-called congenital (present from birth) CMV infection. In Switzerland, this is estimated to occur in 0.5 percent of births and affects around 400 babies nationwide each year. Most of them show no outward signs of the viral infection – but around one in ten of these infected newborns develop symptoms of the disease.

Infection: How are cytomegaloviruses transmitted?

Many pregnant women and new mothers are surprised when they hear about cytomegaly for the first time.
How can a pregnant woman who feels perfectly healthy become infected with CMV?
The virus is usually passed on from person to person through direct contact with bodily fluids or via the respiratory tract.
This can include excretions when changing diapers as well as breast milk, blood, saliva, tear fluid, semen or vaginal secretions.
All of these excreted fluids can contain cytomegaloviruses in infected people.
Parents are more likely to become infected through close contact with their young children.
This is because boys and girls up to the age of four are infected with CMV more often than average, for example in nurseries.
They are then often infectious for a longer period of time – in other words, they can pass on the virus through their bodily fluids (saliva, tears, urine).
Pregnant mothers who already have a small child are therefore at an increased risk of CMV.
A study has shown that in Switzerland the risk of CMV infection is ten times higher for mothers of children who are cared for in day nurseries; in contrast, the risk for nursery teachers is only four times higher.
One possible explanation for this difference is that nursery nurses presumably pay more attention to hygiene regulations than parents at home.
CMV infections that occur during pregnancy can be particularly problematic.
There is a risk that the infected mother will transmit the cytomegalovirus to her unborn baby via the placenta.
In medicine, this type of transmission is called “transmission”.

CMV infection: how high is the risk during pregnancy?

If the first infection of a pregnant woman occurs around the time of fertilization, the risk of transmission to the unborn child is around 20 percent.
If transmission occurs after fertilization but within the first three months of pregnancy, the risk of transmission increases to around 30 percent.
In the last trimester of pregnancy, the probability of cytomegalovirus being transmitted from the mother to the unborn child is even higher.
However, even if the unborn child is infected, this does not necessarily mean that health problems will occur: The risk of this is around 30 percent after transmission at the time of fertilization and 20 percent during the first three months of pregnancy.
Later, after around the 23rd week of pregnancy, the risk of serious damage following an infection decreases even more because the development of the unborn child’s organs is then largely complete.
It can therefore be summarized that the later in pregnancy the infection occurs, the more frequently it is transmitted, but at the same time the less likely it is to have health consequences.
If a pregnant woman was already infected with CMV months before her pregnancy and therefore does not have a primary infection, her baby is usually not at risk.
Unfortunately, “usually” has to be written as – strictly speaking – there is no real immunity to CMV (see below).
The risk of adverse health effects after a cytomegalovirus infection is also low for the pregnant women themselves.
More than 70 percent of women who become infected with CMV during pregnancy feel nothing of this.

Symptoms: What can cytomegaloviruses do?

A CMV infection can have very different effects on those affected.
Whether baby, child or adult: in most cases there are no symptoms at all.
However, very serious health consequences can also occur.
Sometimes babies who become infected in the womb show symptoms before or at birth.
However, they can also appear weeks or months later.
Or even later in life.

• Unborn babies: Serious health problems caused by an infection in the womb include hearing impairment, visual impairment or even blindness and an enlarged liver.
  Physical and mental disabilities can also be the result of a CMV infection.
  Such damage is most likely to occur if the infection takes place in the first trimester of pregnancy; the later the CMV infection occurs, the less likely it is that the unborn child’s organs will be damaged.
• Premature babies: They are particularly at risk.
  If their sensitive and immature organism is attacked by cytomegalovirus, the infection can even be fatal.
• Babies: If babies become infected after birth, the health consequences are usually not serious; an infection may even go unnoticed.
• Pregnant women and new mothers: If they notice their CMV infection at all, the symptoms often resemble the signs of flu.
  They manifest themselves, for example, as fever, fatigue or coughing.
• Healthy children and adults: In most cases, they do not show any symptoms after an infection with CMV.
  Some people affected may show signs of illness that resemble a flu-like infection with fever.
  Only rarely (and then mainly in adults) does pneumonia or liver inflammation occur.
  Three to twelve weeks usually pass between infection and the appearance of the first signs of illness; this is the so-called incubation period.
• People with immunodeficiency: In people with a weakened immune system, cytomegaloviruses can lead to inflammation and damage to various organs.

Diagnosis: How do you recognize cytomegaly?

If a pregnant woman is infected with the cytomegalovirus, the pathogen is not always transmitted to the unborn child.
And even if such transmission does occur, it has no consequences for the majority of babies.
A CMV infection can be detected by examining blood, urine or another bodily fluid in the laboratory.
If it contains certain antibodies that the body has produced to fight off the cytomegalovirus, this is indirect evidence of an infection.
You can also look for traces of protein or genetic material of the virus in the body fluid.
If this is found, it is direct evidence of the CMV infection.

Initial infection, reactivation or re-infection – different risks

Doctors usually want to find out whether the infection is the first infection (“primary infection”) or whether there was a previous infection that is now either becoming active again (“reactivation”; this is comparable to recurring herpes) or a second infection is occurring with a different CMV strain (“re-infection”; this is possible as there are different CMV strains and therefore there is no real immunity as there is with rubella or measles, for example).
This distinction is important in order to better assess certain risks.
For example, the probability of a pregnant woman infecting her baby in the womb is lower with a second CMV infection than with a first infection.
In general, it must unfortunately be said that the data on reactivation and re-infection is less clear and the actual risk can be less clearly defined.
Diagnostics and treatment during pregnancy are therefore currently focused primarily on the more relevant first infections.

CMV infection – ultrasound examination

In some cases, a baby’s CMV infection can be detected by an ultrasound scan before birth.
For example, if the unborn child is unusually small or other abnormalities can be seen on the screen, such as on the brain.
However, this does not always have to be due to a CMV infection; there are also various other possible causes.

Cytomegalovirus in amniotic fluid?

In pregnant women, an examination of the amniotic fluid can also be informative.
If cytomegalovirus can be detected in the amniotic fluid, it is clear that the unborn child has been infected with CMV (the “transmission” described above) – but this does not necessarily mean that there will be any health problems.
If, on the other hand, there is no CMV in the amniotic fluid, the pregnant woman can breathe a sigh of relief: her baby is not infected.
The following applies to the detection of cytomegaly: a combination of different tests and findings can help experts to narrow down the time of infection.
This is particularly important in terms of advice during pregnancy and possible consequences for the unborn child.
As such examinations are challenging due to the special characteristics of CMV, advice from a specialist may be necessary.

Treatment: How is cytomegaly treated?

Once infected with CMV, the pathogens remain in the body for life: it is not possible to eliminate cytomegaloviruses permanently.
However, this does not mean that doctors have to stand idly by and watch a cytomegalovirus infection.
There are two special therapies for a CMV infection:

• Antivirals: These are drugs designed to inhibit the growth of viruses.
  In many cases, they can also be used to treat newborn babies.
• Hyperimmunoglobulins: These are proteins that are obtained, for example, from the blood of donors.
  They contain antibodies against cytomegaloviruses.

Some of these drugs are still being tested and may have side effects.
This applies to both pregnant women and unborn babies, who react differently to the therapy.
For this reason, the counselling of women and the treatment of cytomegaly should be in the experienced hands of doctors who specialize in CMV.

“At the USZ, we train doctors and external gynecologists intensively on the topic at training events. It is important for us to inform women who are pregnant for at least the second time about CMV, as second pregnancies or multiple births in general are more at risk.”

Prevention: How can cytomegaly be prevented?

You don’t have to be ill to infect others – even people who are healthy can carry the cytomegalovirus and transmit it to others.
Pregnant women in particular should be aware of this and be careful.
This is especially true for expectant mothers who already have a child up to four years old; at this age, boys and girls often become CMV carriers.
There is currently no vaccination to prevent CMV infections (due to the various “strains” described above).
If you follow a few hygiene recommendations as a pregnant woman, you can significantly reduce the risk of infection for your unborn child:

• Wash your hands thoroughly: Wash your hands with soap and water after any contact with your child’s bodily fluids.
  This applies to feeding, blowing the nose, changing diapers, washing and wiping away tears.
• Hygiene in the kitchen and bathroom: Use your own crockery and cutlery when eating.
  Do not share towels and washcloths with your child.
  Toothbrushes should never be shared with others.
  Eating children’s food should also be avoided.
• Avoid kissing on the mouth: This is particularly important in the first few months of pregnancy.
  Cytomegaloviruses contained in saliva could otherwise be easily transmitted.
  A crying child should also not be kissed on the cheek when comforting.
• Cleaning surfaces: Clean toilet seats, washbasins and other surfaces on which the child’s bodily fluids are present.

Not only expectant mothers should observe these hygiene rules, but also their partner.
They can also become infected with CMV – and pass the virus on to the pregnant woman unnoticed, for example through kissing or unprotected sexual intercourse.
If a mother carries the cytomegalovirus and gives birth to a premature baby, there is an additional risk: she could infect her immature baby with breast milk while breastfeeding.
If you are pregnant or planning to have a baby, it is best to discuss the subject of cytomegalovirus with your gynaecologist.