what is Cytomegalovirus.
Cytomegalovirus
Cytomegalovirus (CMV) is a common, and usually mild viral illness. However, the severity and duration of symptoms can vary considerably depending on the health and age of the infected individual. There is a small risk of serious complications for babies if the disease is contracted by pregnant women (congenital CMV). People with weakened immune systems may also be at significant risk from cytomegalovirus infection.
More than half of the population is estimated to have been infected with CMV by the time they reach middle age.
Transmission
CMV belongs to the herpes virus family, which also includes viruses responsible for chickenpox, glandular fever and cold sores.
CMV is not considered to be highly contagious. However, any person infected with the CMV virus, be it dormant or an active infection, can transmit the virus to another person. The virus can be carried in body fluids such as urine, tears, saliva, blood, semen, cervical secretions and breast milk.
As with other members of the herpes virus family, CMV remains dormant in the body for life. Reactivation of the virus can occur but this is not common and does not usually result in illness.
Transmission can occur during any close contact that allows the transfer of infected body fluids. Most commonly the virus is spread in respiratory droplets when coughing or sneezing. It can also be spread through sexual contact, intravenous drug use, direct contact with the wet nappies of infected children, blood transfusions (though blood banks stringently screen donors and test the blood to ensure the virus is not present) and organ transplantation. CMV can also cross the placenta.
Children in day care or preschool are a significant risk group. These settings put children in close contact with one another, and children often don't have the personal hygiene practices that would help to prevent transmission of the CMV virus.
Signs and symptoms
CMV is usually a mild disease but the severity and duration of symptoms can vary considerably depending on the health and age of the infected individual.
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. The incubation period of the CMV virus varies but symptoms usually become apparent about three to 12 weeks after exposure to the virus. Duration of symptoms also varies, though on average they last for two to three weeks.
Symptoms may include:
- Fever
- Headache
- Fatigue
- 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 infection. These can be life threatening and may include:
- Anaemia
- Fever
- Hepatitis
- Pneumonia
- Inflammation of the retina in the eye (retinitis)
- Inflammation of the brain (encephalitis)
- Inflammation of the large intestine (colitis).
Congenital CMV
Congenital CMV (where the virus is passed from the mother to the unborn baby before birth) is an important cause of birth defects. 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. Rarely, congenital CMV can cause a miscarriage or the baby to be stillborn.
Some babies with congenital CMV may be born with obvious problems such as:
- Prematurity
- Low birth weight
- Jaundice
- Enlarged liver and spleen
- Lung problems
- Retinitis.
A percentage of these babies, along with some babies who appeared 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.
Babies can also be infected with the CMV virus as they pass down the birth canal during delivery, though this does not usually result in illness. However, babies born prematurely who become infected with the CMV virus during birth are at greater risk of illness and of complications such as pneumonia and hepatitis.
Diagnosis
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 in saliva, urine and tissue samples.
Treatment
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. The use of these medications to treat congenital CMV infections is still being researched.
Prevention
Ensuring that hands are washed often with soap and warm water and are thoroughly dried will help prevent the spread of the virus. This is especially important for pregnant women who work with infants and children.
Other practices that can help to reduce the transmission of the CMV virus include not sharing needles or syringes and engaging in safe sex practices.
Vaccines against CMV are being researched but, at present, no vaccine is available.
