Cytomegalovirus (CMV): symptoms, pregnancy risks and treatment

The NHS says CMV does not usually cause any symptoms and most people do not realise they have it. Tommy's says that if you have a healthy immune system, CMV does not usually cause symptoms, but if it does you may get flu-like symptoms.

The NHS lists the flu-like symptoms some people get the first time they have CMV. It says they usually get better without treatment within about 3 weeks.

• A high temperature.

• Aching muscles.

• Tiredness.

• A skin rash.

• Feeling sick.

• A sore throat.

• Swollen glands.

The NHS says to see a GP if you have symptoms of CMV and you are pregnant, or you have a weakened immune system, for example because you are having chemotherapy. The GP may arrange tests to find out if you have been infected with CMV. Tommy's similarly advises calling your GP if you have symptoms that could be CMV in pregnancy.

Tommy's and the Royal College of Obstetricians and Gynaecologists (RCOG) say testing for CMV in pregnancy is usually offered only if you have symptoms of flu, glandular fever or hepatitis, or if a routine ultrasound scan shows signs that your baby may have CMV.

Tommy's explains that CMV is a common virus and part of the herpes group of viruses, which also includes the viruses that cause cold sores and chickenpox. Once you get CMV the virus stays in your body.

CMV Action says that when CMV causes an infection for the first time it is called a primary infection, after which the virus remains in the body in an inactive state, usually for life. There are many strains, so you can be re-infected with a different one, and any strain can reactivate, especially when the immune system is weakened.

The NHS says CMV is mainly spread through close contact with someone who already has it. You can pass it on through contact with body fluids, including saliva, blood, breast milk, pee and poo, and through sex. It can only be passed on when it is active.

CMV Action says the chance of getting CMV from casual contact is very low, and that direct person-to-person contact is considered the most likely way to catch it. It adds that pregnant women very often catch CMV from the saliva of a toddler.

• You get CMV for the first time. The NHS says young children often get it for the first time at nursery.

• The virus has reactivated because you have a weakened immune system.

• You have been reinfected with a different strain of CMV.

Tommy's says that around 3 to 5 in every 1,000 babies are born with congenital CMV (cCMV). Most do not have symptoms, but around 10 in 100 babies with cCMV will have problems at birth, and around half of those will have lifelong problems, usually including hearing loss. The RCOG says CMV affects 1 in 200 live-born infants in high-income countries and is a major cause of hearing loss and brain damage.

The risk of harm to the baby is greatest if a woman gets CMV for the first time in early pregnancy, in the first 12 weeks, and appears to be very low after that, according to Tommy's and the RCOG. The NHS says pregnant women who work closely with children or already have a young family are more at risk of getting CMV.

The NHS says if CMV is not causing symptoms, you or your baby may not need any treatment. Antiviral medicine may be used to treat babies diagnosed with congenital CMV after they are born, people with a weakened immune system, and people who have had a stem cell or organ transplant. It says treatment weakens the virus and lowers the chance of serious problems, but does not cure the CMV infection.

In otherwise healthy people with flu-like symptoms, treatment is not usually needed, and symptoms get better by themselves within about 3 weeks, according to the NHS.

A blood test can show if you have CMV infection, according to Tommy's. If a scan shows your baby has a condition affecting development that could be caused by CMV, among other things, you will be offered tests such as amniocentesis, where a little fluid is taken from around the baby, to find out if the baby is infected.

Tommy's says that if you have CMV and it has not been confirmed that your baby has it, you should be offered ultrasound scans every 2 to 3 weeks until the baby is born. If the baby has confirmed CMV you should also be offered an MRI scan of the baby's brain at 28 to 32 weeks. The NHS says babies born with congenital CMV may have tests to check their kidneys, liver, brain, eyes and hearing.

The NHS says CMV can cause problems in people with a weakened immune system. CMV Action lists people on chemotherapy, people who have had a transplant, and people living with HIV as being at risk, and says the virus can be a particular risk to people receiving organ and bone marrow transplants because their immune systems are weakened.

The NHS advises seeing a GP if you have symptoms of CMV and a weakened immune system. Antiviral medicines may be used in these groups, as described above.

The NHS says the best way to lower the chance of getting CMV during pregnancy is to follow simple hygiene steps, as there is no vaccine. Tommy's says your midwife will talk to you at your booking appointment about infections like CMV and how to reduce your risk.

• Wash your hands with soap and water, especially after changing nappies, feeding young children or wiping their nose.

• Regularly wash toys or other items that may have young children's saliva or pee on them.

• Avoid sharing food, cutlery and drinking glasses, or putting a child's dummy in your mouth.

• Avoid kissing young children on the mouth.

Tommy's says you can pass CMV to your baby through breast milk, but in most cases this will not harm them. CMV could cause problems if your baby is premature and very low birth weight, or has problems with their immune system. CMV Action says it is rare for full-term babies who catch CMV this way to have problems. Ask your doctor or midwife if you have questions.

On the NHS, a GP or midwife can arrange a blood test for CMV if you are pregnant and have symptoms. If a scan shows signs that your baby may have CMV, Tommy's says you will be offered further tests such as amniocentesis. Babies with confirmed congenital CMV have follow-up appointments to check their hearing and development.

Some people pay for private antibody testing. Because a single result can be hard to interpret in pregnancy, it helps to share it with your midwife or GP so that the timing of infection, the need for further tests and the options in this section can be discussed by someone who knows your history.