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Cytomegalovirus for health professionals

Cytomegalovirus (CMV) is a beta herpes virus that occurs worldwide and humans are the only source of human CMV.

In developed countries, more than half the population carry CMV virus by the time they reach adulthood and this figure is much higher in developing countries.

Most people who acquire the virus after birth experience few or no symptoms.

Cytomegalovirus remains latent in the host for their lifetime after primary infection, and may become active again (reactivation) particularly during times of compromised immunity, including pregnancy.

A person can also have another infection with a different strain of the CMV virus. 

Congenital CMV (cCMV)

If an unborn baby is infected with CMV, some of these babies may develop serious health problems such as hearing loss, developmental delay or learning problems. Congenital CMV is the most common infective cause of congenital hearing loss.

Infection with CMV during pregnancy may also lead to stillbirth or infant death.

CMV and pregnancy

All women who are pregnant, or trying to conceive, should receive information about CMV prevention as part of routine antenatal or pre-pregnancy practice as recommended by the Royal Australian and New Zealand College of Obstetrics and Gynaecology.

New evidence shows that informing pregnant women about reducing exposure to CMV during pregnancy using simple hygiene practices can reduce the incidence of cCMV infection.

The delivery of prevention information to women and their families is strongly supported by SA Health, with the recognition that the level of awareness about cCMV in Australia is relatively low.

Clinical presentation

Infection in children and adults is usually asymptomatic.

Occasionally, symptoms similar to glandular fever such as fever, sore throat, swollen glands, abdomen pain and jaundice can occur.

CMV infection can result in severe disease for:

Mode of transmission

CMV infection can spread in different ways. The virus can be passed from person-to-person, usually through close contact with saliva, breast milk, urine or other body fluid, or through sexual contact with someone with the infection.

Women who become infected with CMV while pregnant may pass the virus to their unborn child.

Babies can also become infected during delivery and from breast milk. Babies who acquire CMV intrapartum, or from their mother's milk, usually have no acute illness, and these infections are not known to cause the central nervous system and sensory disabilities associated with congenital infection. Breastfeeding can therefore be encouraged as it offers many important benefits to mothers and babies.

CMV can also be transmitted during blood transfusions and organ transplants.

A person can have a primary infection (an infection with CMV for the first time), or a return of a previous CMV infection (reactivation), or may have another infection with a different strain (type) of the virus.

The virus is often shed for months in urine or saliva following infection in healthy children and adults.

Infants and immune suppressed adults can shed the virus for months to years following infection or reactivation of infection.

Incubation period

3 to 12 weeks.

Diagnosis

Diagnosis in infants is made by growing the virus, usually from urine.

Diagnosis in adults is more complicated and usually requires growing the virus, blood tests or PCR (polymerase chain reaction) tests in a pathology laboratory.

Routine serological screening for CMV in pregnancy is not recommended, as past infection with CMV does not mean complete protection against reinfection or congenital CMV.

Pre-pregnancy or early pregnancy screening may be considered for women who have frequent contact with large numbers of very young children (eg childcare workers) as per the NHMRC endorsed April 2019 recommendations.

The need for screening for CMV should be a discussion between healthcare providers and patients on an individual basis.

Serological and virological testing for CMV should be performed when a pregnant woman develops an illness, typically fever, fatigue, and headache, not attributable to another specific infection, or when imaging findings (ultrasound or MRI) are suggestive of fetal cytomegalovirus infection.

Treatment

Antiviral medications may be used to treat those infected, including babies.

When congenital CMV infection is suspected on the basis of maternal serology or fetal ultrasound abnormalities, a referral to a maternal fetal medicine specialist, or specialist with expertise in perinatal infections is recommended.

Prevention

  • There is currently no effective vaccine to prevent CMV infection.
  • Exclusion from childcare, preschool, school or work is not necessary.
  • Pregnant women can reduce their risk of being infected with CMV if they:
    • Do not share food, drinks, or utensils used by children (under the age of 3 years).
    • Do not share a toothbrush with a young child.
    • Do not put a child’s dummy/soother in their mouth.
    • Avoid contact with saliva when kissing a child (“kiss on the forehead not on the lips”).
    • Thoroughly wash hands with soap and water for 15-20 seconds, especially after changing nappies or feeding a young child or wiping a young child’s nose or saliva.
    • Clean toys, countertops and other surfaces that come into contact with children’s urine or saliva with a simple detergent and water.

Useful resources for health professionals

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