Cytomegalovirus (CMV) is a common and usually mild viral illness. Most people are unaware that they have CMV because it rarely causes symptoms in healthy people.
However, people with weakened immune systems and pregnant women (because of the risk of complications for babies) should see a doctor if they have flu-like symptoms or think they may have been exposed to CMV.
CMV belongs to the herpes virus family, which also includes viruses responsible for chickenpox, glandular fever and cold sores. Like these other conditions, the virus remains in the body for life. Reactivation of the virus can occur but this is not common and does not usually result in illness.
CMV is not considered to be highly contagious. However, a person with an active CMV infection can transmit the virus to another person though close contact that allows the transfer of body fluids such as urine, tears, saliva, blood, semen, cervical secretions, and breast milk.
Most commonly the virus is spread in respiratory droplets spread by an infected person coughing or sneezing.
Children in day care or preschool are a significant risk group. These settings put children in close contact with one another, and children often do not have the personal hygiene practices that would help to prevent transmission of the CMV virus.
The incubation period of the CMV virus varies but symptoms usually become apparent about three to 12 weeks after exposure to the virus.
Signs and symptoms
Most healthy individuals who have a CMV infection will not have symptoms. However, when symptoms are present, they are often similar to those of glandular fever. Severity and duration can vary but, on average, will last for two to three weeks. Symptoms may include:
- Muscle aches
- Enlarged glands
- Sore throat
- Enlarged spleen.
Individuals with weakened immune systems (such as people with HIV infection, organ transplant recipients, or cancer patients) are at greatest risk of serious complications of CMV. These can be life threatening and may include:
- Inflammation of the retina in the eye (retinitis)
- Inflammation of the brain (encephalitis)
- Inflammation of the large intestine (colitis)
- Inflammation of the liver (hepatitis).
Congenital CMV (where the virus is passed from the mother to the unborn baby before birth) can be a cause of birth complications. It is usually only a risk when the mother develops a CMV infection for the first time during pregnancy. Most babies will not become infected with the virus and, of those that do, only a small percentage will suffer serious complications.
Some babies with congenital CMV may be born with obvious problems such as:
- Low birth weight
- Enlarged liver and spleen
- Lung problems
A percentage of these babies, along with some babies who appear perfectly healthy at birth, may go on to develop complications such as hearing and sight impairments and developmental problems. In some cases, these complications may be severe.
Rarely, congenital CMV can cause a miscarriage or the baby to be stillborn.
Perinatal CMV is when babies become infected with CMV from their mother as they pass down the birth canal, during delivery or through breast feeding. Such infection does not usually result in illness but babies born prematurely can be at greater risk of illness and of complications with their lungs and liver.
It is estimated more than half of the population will be infected with CMV by the time they reach middle age. However, the signs and symptoms of CMV are not usually severe or specific, so the infection is rarely diagnosed.
Individuals infected with CMV will develop antibodies (special proteins that help fight and destroy foreign bodies such as viruses). These antibodies can be detected in the blood, so blood tests can be used to diagnose CMV infection. It is usual for two blood samples to be taken two weeks apart before an accurate diagnosis is made. To diagnose active infection, CMV can also be cultured from saliva, urine, and tissue samples.
Testing pregnant women for CMV infection can be important. Pregnant women who have already developed CMV antibodies have a small chance of a reactivation of CMV that might infect their unborn children. A prenatal test (amniocentesis) can determine whether the foetus has been infected should a new CMV infection be detected during pregnancy.
When the CMV infection results in a mild glandular fever-like illness, bed rest is often all that is required. Drinking plenty of water will help to relieve a sore throat and prevent dehydration. Paracetamol to treat fever and discomfort may also be beneficial. As CMV is caused by a virus, antibiotics will be of no benefit in combating it.
In cases of serious CMV infections in people with weakened immune systems, antiviral medications may be administered. These medications, such as ganciclovir and foscarnet, are usually given as an infusion into the blood stream but can also be given in tablet form. Antiviral medications can reduce the length of illness and its severity but do not cure CMV.
The use of these medications to treat congenital CMV infections is still being researched. Antiviral therapy has been shown to improve hearing and some development outcomes in infants with symptoms of CMV.
Ensuring that hands are washed often with soap and warm water and are thoroughly dried will help prevent the spread of CMV. Not sharing food, eating utensils, and drinking glasses, and avoiding close contact with anyone who has the infection will also help to prevent spreading the virus. This is especially important for pregnant women who work with infants and children.
Vaccines against CMV are being researched but, at present, no vaccine is available.
KidsHealth (2018). Cytomegalovirus (CMV) (Web Page). Philadelphia: The Nemours Foundation, Inc. https://kidshealth.org/en/parents/cytomegalovirus.html?ref=search# [Accessed: 16/07/20]
Marisco, C. & Kimberlin, D. W. (2017). Congenital cytomegalovirus infection: advances and challenges in diagnosis, prevention and treatment. Ital J Pediatr. 2017;43(1):38
Mayo Clinic (2020). Cytomegalovirus infection (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/cmv/symptoms-causes/syc-20355358 [Accessed: 16/07/20]
NHS Choices (2017). Cytomegalovirus (CMV) (Web Page). Redditch: National Health Service (NHS) England. https://www.nhs.uk/conditions/cytomegalovirus-cmv/ [Accessed: 16/07/20]
O’Toole, M.T. (Ed.) (2017). Cytomegalovirus (CMV). Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.
O’Toole, M.T. (Ed.) (2017). Cytomegalovirus inclusion disease (CID). Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.
Last reviewed – July 2020
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