CMV, or Cytomegalovirus, is a common virus that can infect people of all ages. Most healthy adults and children who become infected will have no signs or symptoms and no long term effects from CMV.  However, CMV can pose serious problems to unborn babies if a  woman catches it during pregnancy .  In fact congenital CMV (when the infection is passed from mother to baby across the placenta) is one of the most common non-genetic cause of inner ear hearing loss and a major cause of  childhood disability.  

Despite this, there is very little awareness of CMV and the facts are often misunderstood.  A diagnosis of CMV can be stressful and confusing.

CMV is the most common infection passed from mother to unborn baby.

Who is at risk of CMV?

CMV can infect people of all ages. Most healthy adults and children will have no signs or symptoms and no long term effects. However, it can pose serious problems if a woman catches CMV during pregnancy and passes it on to her unborn baby, particularly if this happens during early pregnancy. Others at risk include people with low immune systems, for example, people on chemotherapy, or who have had a transplant or who are living with HIV infection.

The majority of babies born with cCMV will not have any symptoms at birth and will not suffer any long term problems. However, ten babies are born each day in the UK with CMV and two or three of these babies will have long-term problems  – that is 1000 babies every year. What is the difference between CMV & congenital CMV?

Anyone can become infected with CMV. Congenital CMV  (cCMV)is when CMV infection is transferred from the mother to the unborn baby across the placenta during pregnancy.


The main ways of catching CMV are: 

Person-to-person contact

CMV is spread from one person to another by close and prolonged contact with bodily fluids such as urine, saliva, blood, faeces, tears, breast milk, semen and cervical secretions. You can catch CMV by kissing, sexual intercourse, sharing eating and drinking utensils, and sharing mouthed toys.   The chance of getting CMV infection from casual contact is very low.

Mother to unborn baby

CMV can be transmitted to the developing baby across the placenta, causing congenital CMV.  Very often pregnant women catch CMV from the saliva of a toddler, therefore care should be taken not to eat leftover food, drink from the same cup, share utensils or kiss on the lips.  It can also be caught through contact with urine, so hands should be thoroughly washed after changing a nappy.

Mother to newborn baby

CMV can be transmitted to newborns through the mother’s breast milk or the process of giving birth. It is rare for full-term babies who catch CMV in this way to have problems. However, premature babies or very low birth weight babies can be affected.


CMV may be spread to those receiving organ and bone marrow transplants. The virus can be a particular risk to these patients as their immune system is compromised or weakened.


Patients who receive a blood transfusion from a donor with CMV infection may acquire CMV themselves. However, donor blood is routinely treated in the UK to reduce these risks and CMV negative blood is recommended for some at-risk groups. People who have a normal immune system are unlikely to have health problems as a result of CMV infection.

What happens in the body during a CMV infection?

When CMV causes an infection for the first time it is called a primary infection. Just as with all infections, the body begins to fight CMV by producing antibodies (protective proteins) and immune cells. While there is an active infection in the body, CMV will be excreted or shed in bodily fluids. However, after infection the virus remains  in the body in an inactive state, usually for life. CMV antibodies will be present for life as well.

There are many different strains of CMV. Even if a woman has antibodies against one strain of CMV, she can  still get re-infected with a different strain. The body will fight the virus and produce new antibodies just as with a primary infection.

It is possible for any strain of CMV to reactivate or act like a new infection. This type of infection is a recurrent infection and may occur at any time, but especially when the immune system becomes altered or weakened. When reactivation occurs, CMV antibody levels may increase and active CMV will be present in bodily fluids (viral shedding).

Are some people immune to CMV?

If you have had CMV before then you will be immune to that strain of the virus. However, there are lots of different strains of CMV and you will not have natural protection against all of these.

How long does the virus stay on surfaces?

The CMV virus survives on different surfaces for different periods of time. For example, it survives at least 15 minutes on hands, longer on plastic and shorter on wood.

Studies suggest that it  can survive on surfaces long enough for people to pick it up.  However, direct transmission through person-to-person contact is still considered the most likely way for people to catch it.