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.
See Cytomegalovirus - causes for more information about how the virus is passed on.
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 the UK 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
Outlook
Unlike many viral infections, CMV usually causes few if any symptoms. Most people do not know they have (acquired) an infection.
See Cytomegalovirus - symptoms for more information about possible symptoms.
CMV can be more serious when it develops or reoccurs in certain vulnerable groups of people:
- people with a weakened immune system, particularly those with HIV or who have recently had an organ transplant or a bone marrow transplant
- unborn and newborn babies
HIV
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, may also occur.
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.
Due to improvements in diagnosis and screening such infections are quite rare in adults, and though they are more common in children, effective treatment is available.
Unborn and newborn 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. For them, however, the infection can be serious, even fatal. It is estimated that between 10-30% of very young babies (less than 28 days) with a CMV infection will die. The risk can be much higher in premature babies.
Babies that do survive may develop 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.
See Cytomegalovirus - prevention for more information on how to prevent congenital CMV.
