What is Cytomegalovirus?

Cytomegalovirus (CMV) belongs to the herpes virus family. Infection with CMV is very common. Between 50% and 80% of people in the United States have had a CMV infection by the time they are 40 years according to the Centers for Disease Control and Prevention (CDC).

Who is affected by cytomegalovirus?

Infection in children may occur in early childhood, especially those in childcare and preschool. The infection is seldom serious in otherwise healthy children and adults.

What are the symptoms of cytomegalovirus?

There may be mild symptoms that are similar to those seen in mononucleosis and last for a few weeks at the most. However, some groups are at a higher risk of complications from CMV infection. These include pregnant women as it can harm unborn babies and those with a suppressed immune system due to disease or drug treatment, such as organ transplant recipients or people infected with HIV.

About the virus

CMV is a member of the herpesvirus group, which includes herpes simplex virus types 1 and 2, varicella-zoster virus (which causes chickenpox), and Epstein-Barr virus (that can cause infectious mononucleosis).

The virus may remain dormant or sleeping within the body over a long period. It leads to an initial CMV infection, which has a few symptoms. The virus remains dormant in the body, reactivating only when the body’s immune system is weakened.

The name is derived from Greek word “cyto” meaning cell and “megalo” meaning big. CMV is also known as HCMV or Human Herpesvirus 5 (HHV-5). CMV belongs to the ''Betaherpesvirinae'' subfamily of ''Herpesviridae'', which also includes Roseola virus.

Name	Abv.	Host
''Cercopithecine herpesvirus 5''	(CeHV-5)	African green monkey
''Cercopithecine herpesvirus 8''	(CeHV-8)	Rhesus monkey
''Human herpesvirus 5''	(HHV-5)	Humans
''Pongine herpesvirus 4''	(PoHV-4)	?
''Aotine herpesvirus 1''	(AoHV-1)	(Tentative species)
''Aotine herpesvirus 3''	(AoHV-3)	(Tentative species)

CMV pathogenesis and symptoms

Once a person has had a CMV infection, the virus usually lies dormant (or inactive) in the body, but it can be reactivated. Reactivation occurs when the immune system is weakened.

Symptoms vary according to age and health of the patient. Some of the symptoms include:

Infants who are infected before birth usually show no symptoms of a CMV infection after they are born. They may develop severe symptoms including hearing loss, blindness, neurological, and developmental problems over time. Some infants may have other symptoms at birth including premature delivery, jaundice, enlarged liver and spleen, small head or microcephaly, being small for gestational age, seizures, rash, and feeding difficulties.
Newborns affected with the virus after birth by passing through the birth canal of an infected mother or by consuming breast milk from a mother with the virus or due to contact with an infected person usually show no symptoms of CMV infection. Some may develop pneumonia and other complications. If the babies have been born prematurely they are at a greater risk of complications.
Young children with the infection may develop insignificant illness. In some cases there may be complications like pneumonia, hepatitis, or a rash. Older children and healthy adults may have a few days or couple of weeks of mild illness with muscle pain, fatigue, headache, fever, and enlarged liver and spleen.
Those with a weakened immune system may develop severe complications like involvement of lungs, nervous system, gastrointestinal tract, and the eyes.

Duration of illness

Serious CMV infections before birth may cause developmental problems that affect a child for a lifetime. However, infection that occurs later in life may last a few weeks at the most.

Transmission of infection

Transmission requires close contact. The virus is spread via fluids like saliva, breast milk, vaginal fluids, semen, urine, and stool. It also can be transmitted via blood products and donated organs.

Infection may be transmitted to the new born baby from the passage through infected mother’s birth canal, via breast milk from infected mother or contact with another infected person or blood transfusion.

Among young children kids, the virus is commonly spread in childcare centers or preschool. These setting allow for spread through indirect contact, especially though contaminated toys. Infected kids may then spread the virus to their families.

Diagnosis and Treatment

CMV is diagnosed by taking a sample of fluids from the infected person’s throat, urine, blood, or other body tissues or fluid. Serological tests can be applied to look for certain antibodies to CMV infection. Their presence can signal an active CMV infection. Special viral DNA-detecting tests are also sometimes used to diagnosis CMV infection.

Currently, no specific treatment is available or recommended for otherwise healthy people with CMV infection. In those who are particularly vulnerable for complications like newborn infants, organ-transplant patients, and people being treated for cancer or who have immune disorders such as AIDS, some antiviral medications may be used intravenously. Oral antiviral medication also may be used at home once the infection is under control and the patient is stable. Some of the drugs used include CMV-immune globulin (CMV-IVIG) and the antiviral drug Ganciclovir.

Prevention of infection

There are at present no vaccines to prevent CMV infection. For those who have close contact with children, especially pregnant women or women, simple measures like hand washing may help. Other measures include are not sharing eating utensils, avoidance of intimate contact with anyone who has a CMV infection etc.

However, a mother with the infection is advised not to stop breast feeding as the benefits of breastfeeding are believed to outweigh the risks of passing CMV to the baby. Blood and organs before donation need to be screened for the virus to prevent spread.