Cytomegalovirus (CMV)

Cytomegalovirus (CMV) is a common virus that is usually harmless. Sometimes it causes problems in babies if you catch it during pregnancy (congenital CMV).

What is CMV?

CMV is similar to the herpes virus that causes cold sores and chickenpox.

Once you have the virus, it stays in your body for the rest of your life.

Your immune system usually controls the virus and most people don't realise they have it.

How CMV is spread

CMV is mainly spread through close contact with someone who already has CMV. It can be passed on through body fluids including saliva, blood and urine.

CMV can only be passed on when it is "active". This is when:

• you catch the virus for the first time – young children often get CMV for the first time at nursery
• the virus has "re-activated" – because you have a weakened immune system
• you've been re-infected – with a different type (strain) of CMV

Pregnant women can pass an "active" CMV infection on to their unborn baby. This is known as congenital CMV.

CMV doesn't always cause symptoms

Some people get flu-like symptoms the first time they catch CMV, including:

• a high temperature of 38C or more
• aching muscles
• tiredness
• feeling sick
• sore throat
• swollen glands

If you do have symptoms, they normally get better on their own within about 3 weeks.

See a GP if you have flu-like symptoms and:

• you're pregnant
• you have a weakened immune system – for example, because you're having chemotherapy

If your GP is worried about your or your babies' health they can arrange tests to find out what's causing your symptoms.

How CMV is treated

CMV that isn't causing symptoms doesn't need any treatment.

There's currently no treatment for CMV in pregnancy and in most cases the virus doesn't cause any problems for your baby.

Antiviral medicine can be used to treat:

• babies diagnosed with congenital CMV after they are born
• people with a weakened immune system

Treatment should help to weaken the virus and reduce the chance of serious problems – but it doesn't cure CMV infection.

Babies born with congenital CMV need to stay in hospital until the antiviral treatment finishes.

How to reduce the risk of CMV in pregnancy

The best way to reduce the risk of catching CMV during pregnancy is with some simple hygiene measures:

• wash your hands using soap and hot water – especially after changing nappies, feeding young children or wiping their nose
• regularly wash toys or other items that get young children's saliva or urine on them
• avoid sharing food, cutlery, drinking glasses or dummies with young children

There's currently no vaccine for CMV.

If you'd like to know more about CMV, you might find these links useful:

• CMV: your questions answered (PDF download, 942kb) – CMV Action
• Congenital CMV – Great Ormond Street Hospital (GOSH)

You could also contact the UK charity CMV Action for more help and support if you or your child are diagnosed with CMV.