What is Cytomegalovirus?
Cytomegalovirus (CMV) is an extremely common virus which is part of the herpesvirus family. There are various different strains of CMV. CMV infection seldom causes any symptoms in healthy individuals. Infected individuals carry the virus lifelong but it remains suppressed by the immune system in healthy individuals and they have no long term health complications.
However, CMV can cause symptoms and potentially dangerous, even life-threatening illness and complications in individuals with weakened immune systems, such as infants whose immune systems are not fully developed, or individuals on immunosuppressive or chemotherapy and individuals with poorly controlled HIV.
How common is CMV?
According to the US Centers for Diseases Control and Prevention, almost one third of children will be infected by CMV by age 5, and more than half of adults will have been infected by the time they reach age 40.
How is CMV spread?
CMV is transmitted through body fluids like blood, semen, vaginal fluids, saliva, urine and breast milk.
Transmission can occur when infected bodily fluid comes into contact with someone’s mucosa e.g. the eyes, lining of the mouth, or through sexual contact. An infected individual can transmit the virus during periods of activation- when it is not adequately suppressed by one’s immune system. Other modes of transmission include vertical transmission from mother to infant before or during birth, or through breastfeeding. One can also acquire CMV through blood transfusions or organ transplants.
What are the symptoms and possible complications of CMV?
In most healthy individuals, CMV may not cause any symptoms at all. However, during the initial infection, some individuals may experience symptoms of fever, fatigue, myalgia (muscle ache), swollen lymph nodes and a sore throat. These symptoms are very similar to that of infectious mononucleosis or glandular fever. In healthy individuals, reactivation of the virus very rarely occurs as the immune system keeps it in check.
In immunocompromised individuals, CMV can affect and cause symptoms involving various organs including the eye, liver (hepatitis), and the gastrointestinal tract (esophagus, stomach, intestines).
CMV infection during pregnancy can lead to severe consequences for the unborn infant – infants who are infected during pregnancy (known as congenital CMV) may have problems affecting various organs including the brain, ears, liver, and lungs (see below for more on congenital CMV).
What is congenital CMV?
Congenital CMV occurs when CMV is transmitted from a pregnant mother to her unborn foetus during pregnancy. This can occur if a pregnant woman has a primary (new) CMV infection, or is reinfected with a new strain of CMV, or if she suffers a reactivation of a preexisting CMV infection. The risk of severe complications is highest if infection occurs during the first trimester of pregnancy.
Some of the effects of congenital CMV infection are apparent at birth. This includes possible jaundice, hepatosplenomegaly (enlargement of the liver and spleen), inflammation of the eye retina (retinitis), seizures, microcephaly (small head) and low birth weight.
Some complications can be long term/life-long, including hearing and vision loss, intellectual disability and seizures.
Who is at risk of CMV?
CMV can cause serious health problems in susceptible individuals:
1) Infants who are infected during pregnancy (congenital CMV)
2) Infants born premature or with very low birth weight
3) Immunocompromised individuals e.g. organ transplant recipients or individuals with HIV.
CMV and HIV
Not all individuals with HIV are at risk of CMV disease. Only individuals with a low CD4 (T cell – a form of immune cell) count are at risk. This usually occurs only if they are not on, or have failed to respond to antiretroviral therapy. Either re-infection with a new strain of CMV, or reactivation of an existing CMV infection can result in symptoms.
The most common manifestation is CMV retinitis – inflammation of the retina of the eye, resulting in visual disturbances or visual loss. CMV can also cause inflammation of the esophagus (esophagitis), resulting in symptoms like pain on swallowing, and inflammation of the colon (colitis), causing diarrhoea, abdominal pain and weight loss.
In rarer cases, CMV can affect the brain and nerves, causing symptoms like dementia, confusion, numbness and weakness.
How does one test for CMV?
In symptomatic adults, antibody blood tests can be used to diagnose CMV infection. Other special tests may be necessary to determine organ involvement if there are symptoms to suggest this.
For infants with CMV, a urine or saliva sample is usually used to test for infection. Testing for congenital CMV has to be done within 3 weeks after birth.
What is the treatment for CMV infection?
Healthy individuals with no symptoms do not require any treatment for CMV. However, in immunocompromised individuals who develop symptoms or in cases of congenital CMV infection, anti-viral medications can be used to treat and suppress the virus. In individuals with HIV, adherence to antiretroviral therapy and maintaining good CD4 counts is crucial. Treatment with anti-virals against CMV is not recommended unless there is evidence of CMV disease affecting an organ (end-organ disease).
Speak to our doctors to find out more about Cytomegalovirus (CMV) and it’s available testing or treatment options.
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