Cytomegalovirus

What causes it?

Cytomegalovirus is a type of herpes virus. It's so common that, if tested, most people would be found to have it. However, it usually passes unnoticed.

The virus can be passed on in many ways. It's often carried in the air in tiny fluid droplets when someone coughs or sneezes. It can also be transmitted during sexual intercourse, organ transplants and blood transfusions. In developed countries, blood supplies are screened for CMV when they're to be used for those at greatest risk from the infection.

What are the symptoms?

When they do occur, the symptoms - fever, tiredness, a sore throat, upset stomach with diarrhoea, nausea and vomiting - are similar to those of other viral infections and often attributed to another cause. In teenagers, for example, the symptoms may be mistaken for glandular fever.

Who's affected?

In most cases, CMV is harmless, but for some people infection can have disastrous consequences.

People with weakened immune systems (because of HIV, for example) can suffer serious illness. They may experience high fever for two or three weeks, accompanied by hepatitis and jaundice.

Other serious complications include pneumonia, inflammation of the brain (encephalitis) and blindness as a result of inflammation of the retina at the back of the eye.

CMV remains in the body for life. For those with strong immune systems, it remains inactive. If the immune system is weakened through illness or medical treatments, CMV may be reactivated, causing further medical problems and distress.

If a pregnant woman becomes infected with CMV for the first time, the virus may pass through the placenta and infect her unborn baby. If this happens early in pregnancy, the risk of miscarriage increases, as does the chance of the baby being born with malformations. For example, CMV infection in the womb is the leading cause of congenital deafness.

If the infection is contracted later in pregnancy, stillbirth and premature labour are more likely. A newborn baby may suffer severe illness shortly after birth - jaundice, enlargement of the liver and blood disorders.

What's the treatment?

In most cases, CMV isn't treated because it doesn't cause any symptoms and goes unnoticed.

If symptoms are severe and CMV infection is confirmed with a blood test, antiviral drugs may be given.