Infection with cytomegalovirus (CMV)

The cytomegalovirus belongs to the family of herpes viruses. The virus remains in the body lifelong after the initial infection. It is “dormant” in the body’s cells and can be reactivated and multiply under certain circumstances. Most people with a healthy immune system do not become ill from infection with CMV.

However a CMV infection can be harmful for fetuses, premature babies and people with immune deficiency, and can cause organ damage in fetuses. The infection can cause serious complications which are sometimes fatal in premature babies and people with immune deficiency.

Pregnant women can pass on the cytomegalovirus to the fetus, particularly if they are infected for the first time during the initial trimester. Women trying for a baby can take a test before a planned pregnancy to see whether they have already had a CMV infection.

People are frequently infected with CMV for the first time when they are still children but it can occur at any age. Most people with a healthy immune system do not have any, or only have mild symptoms. These include lassitude, high temperature, coughing and occasionally elevated liver enzyme levels.  

Symptoms generally occur 4 to 6 weeks after infection (incubation period).  

The potential consequences for at-risk groups include:  

• high temperature 
• pneumonia 
• hepatitis, enteritis and/or esophagitis 
• choroiditis, retinitis, potentially causing blindness 

If the dormant virus is reactivated and the person becomes ill, symptoms may be mild or severe. 

It can cause growth abnormalities, brain damage, damage to the nervous system and hearing impairment in children who were infected in the womb. It can take some time for these conditions to appear after birth. 

Following infection the cytomegalovirus is found in tears, saliva, urine, genital secretions, blood and breastmilk. So it is mainly transmitted from person to person via saliva, close physical contact such as kissing and sexual intercourse, or via breast milk. This is referred to as droplet (airborne) transmission or transfer by touch. Infants up to 3 years old in particular can shed large amounts of the virus. 

However, certain blood products and transplanted organs can also transfer CMV to other people. 

Expectant mothers can pass on CMV to their unborn child, especially if this is the first time they have been infected, but also if the virus is reactivated during pregnancy. The risk is particularly high in the first trimester. 

The initial infection or reactivation of the virus can have serious consequences for people with a high risk of a severe cytomegalovirus infection.

The factors that affect a person’s risk of being infected include infant care, poor hygienic conditions and number of sexual partners. The proportion of people infected with CMV in the general population can only be estimated. Tests of blood donors indicate that just under half have CMV antibodies in their blood. That means they have already had their initial CMV infection. 

Over half of all pregnant women and just under a quarter of all people with a kidney transplant in Germany have no cytomegalovirus antibodies. They are therefore susceptible to their initial CMV infection. 

CMV is the commonest infection passed on to fetuses from pregnant women.

Infection with CMV is harmless for people with a healthy immune system. Since there is no vaccine against CMV, people at a higher risk of severe CMV infection need to protect themselves. They include people with immune deficiency or receiving immunosuppressants as well as pregnant women who test CMV-negative. 

Around one in 200 women become infected with CMV for the first time during pregnancy. An initial infection is not harmful for them. However it is a risk to the fetus, particularly in the first three months of pregnancy, and can cause severe, permanent harm, particularly to the brain and nervous system.  

Precautions for CMV-negative pregnant women  

Good hygiene can reduce the risk of an initial infection with CMV during pregnancy. The recommendations below apply to pregnant women who have not yet had their initial CMV infection or do not know whether they have CMV antibodies in their systems. The recommendations are particularly aimed at women who have high levels of contact with children at work.  

Hygiene recommendations: 

• thorough, frequent handwashing, particularly after changing diapers, washing, feeding, wiping away tears, cleaning children’s noses and contact with toys that children have put in their mouths
• cleaning objects and surfaces that have come into contact with infants’ urine and saliva
• avoiding kissing babies and infants on the mouth or cheek  
• not sharing crockery, cutlery, towels and cloths with other people

Women trying for a baby can have a blood test for CMV antibodies. Under the current maternity service guidelines, the German statutory health insurance providers are not obliged to cover the costs of the test. Some do, however, so it’s worth asking. The cost is around €30 for those paying themselves. 

Contact between mothers who have had a CMV infection and babies  

If mothers have already had an initial CMV infection, the virus can be reactivated during breastfeeding and passed on to the baby via breast milk. This isn’t a problem for babies brought to term, but there is a risk of complications developing in premature babies. Special precautions must therefore be taken for premature babies at hospital. 

Have blood products been screened for CMV? 

Bone marrow donors are tested for active and prior infections with CMV. This is not required for blood products: blood products that do not contain any white corpuscles are classed as safe even without a test.

Donor organs 

Organ donations are also tested for CMV antibodies, as infection of a transplant recipient with CMV can cause severe illness and even rejection of the transplanted organ because of the immunosuppressant drugs they are given.

Organs from CMV-positive donors are not normally given to CMV-negative recipients. However they can be transplanted into CMV-positive recipients if precautionary drug treatment is provided. So a positive test for CMV in an organ donor does not mean the organ cannot be transplanted.

An infection can be diagnosed in the laboratory, either directly by detecting the virus, its components or genetic material, or indirectly by detecting antibodies. 

Direct CMV tests such as urine, saliva or blood tests, are the preferred option for an acute initial infection or reactivation from the “dormant state” and in people with immune deficiency. Indirect antibody tests are used particularly in people with a healthy immune system to detect whether they have had an initial infection. The type of CMV antibody detected is used to determine whether the initial infection occurred recently or a long time previously.

Patient with a healthy immune system do not need any CMV-specific treatment.  

Patients at a high risk of becoming ill from a CMV infection are treated with virostatics. These are drugs which inhibit viral replication. They include, for example, ganciclovir, cidovovir, foscarnet and valganciclovir.  

Newborns infected with CMV prior to birth should only be given virostatics to treat CMV in agreement and cooperation with a specially qualified newborn center. Pregnant and breastfeeding women should not be treated for CMV with virostatics.

The prophylactic or therapeutic value of transfusion of CMV antibodies (hyperimmunoglobulin) is disputed.