Congenital Cytomegalovirus: The Most Common Congenital Infection That You Have Never Heard Of

infantDown Syndrome. Fetal alcohol syndrome. Spina bifida. Most people have heard of these well know congenital conditions, and know at least in a general sense that they have profound and lasting effects on the children born with them as well as their families. Unfortunately, people are much less aware of a congenital infection that is more common that any of these and affects more infants than all three of the conditions listed above. In fact, this congenital infection causes more cases of congenital disease than all of the 29 conditions currently screened for in most American states combined (1; 2), and yet it is not widely known by the general public. Cytomegalovirus, or CMV, is the most common congenital viral infection in developed countries (3; 4), and the leading cause of congenital sensorineural hearing loss and psychomotor retardation (1).

CMV Infection

A ubiquitous herpesvirus, CMV is spread through close personal contact with body fluids such as saliva, blood, urine, genital secretions and breast milk. In the United States, 90% of the population has developed an immune response to CMV by their 8th decade of life (3). Although infection is often time asymptomatic, or accompanied by only mild symptoms, infection in immunocompromised individuals, including newborns, can be devastating. Infants infected with CMV in utero can develop a number of different conditions as a result including vision loss, mental retardation, seizure disorder, cerebral palsy, visual deficits and developmental delay (3). Fetal infection with CMV from a new or reactivated maternal infection can occur at any point in pregnancy. In the developed world, 0.6–0.7% (1 in every 100 to 150) of all babies are born with congenital CMV. According to the CDC, 1 in 750 babies born in the United States develop permanent problems as a result of congenital CMV infection (4).

Cytomegalovirus, or CMV, is the most common congenital viral infection in developed countries, and the leading cause of congenital sensorineural hearing loss and psychomotor retardation.

Babies born with congenital CMV fall into one of two categories:  symptomatic or asymptomatic. An estimated 12.7% of infants with congenital CMS are born symptomatic (1). Infants with symptomatic CMV infections can show a range of symptoms from mild nonspecific symptoms to death. Commonly seen symptoms include a petechial rash, jaundice and enlarged spleen or liver. Neurological abnormalities can include microcephaly and lethargy; ophthalmological indicators include chorioretinitis and/or optic atrophy (5). Looking at the percentages for infants with symptomatic CMV infection: 4% die, 50% have motor or cognitive deficits, 50% have hearing loss and 22% have vision impairment (1).

The long-term effect of congenital CMV infection on asymptomatic infants is harder to determine. A positive identification of an in utero infection relies on detection by culture or PCR using samples (saliva or urine) obtained during the first two weeks of life, as these tests cannot distinguish between intrauterine and postnatal infections beyond two weeks. Antigen testing (pp65 antigen) can be performed for the first 3 weeks of life. Since symptoms may not be apparent for some time after birth, it is difficult to identify how many asymptomatic infants suffer permanent sequelae, but the estimate is that at least 11% of these infants will suffer some amount of hearing loss (1).

Risk of CMV infection can be greatly reduced by making woman aware of the possible long-term consequences of infection as well as the most likes cause for infection (exposure to the urine or saliva of children who are shedding CMV virus) combined with educating them about primary prevention strategies, which include limiting exposure to children and careful hand washing after contact with children. These precautions are particularly important for women who test CMV-seronegative, as babies of woman who experience a primary CMV infection while pregnant are at the highest risk of life-long consequences.  Unfortunately, the risks of congenital CMV infection are not well known. In fact, a public survey conducted in 2013 showed that only 7% of men and 13% of women had heard of congenital CMV (6).

The Benefits of Prenatal Maternal Screening

Screening mothers for CMV status could identify at-risk pregnancies, allowing physicians to monitor both mother and fetus more closely and make it more likely that congenitally infected infants born asymptomatic would receive medical intervention earlier. Unfortunately, there is not an established method for how to treat maternal primary infections, nor is there a way to determine the individual prognosis of the mother or fetus following infection. In addition, maternal screening would identify on a fraction of the fetuses at risk, since an estimated two-thirds of CMV-infected infants in the United States are born to women who are seropositive prior to becoming pregnant (1)

The Argument for Infant Screening

Screening infants at birth for genital CMV infection could have a profound positive life-long effect. Although there is no treatment that will prevent sequelea in all infants with congenital CMV, early treatment can have long-term benefits. Studies have shown that treatment using the antiviral agent, ganciclovir, provides long-term neurodevelopmental benefit for some infants with congenital CMV infection (7; 8). In addition to the potential benefits of ganciclovir treatment, identifying CMV positive infants would allow families and doctors to watch for signs of hearing loss and other affects, eliminating the extensive (and costly) testing that children identified with hearing loss typically undergo.

Summary

CMV is the most common congenital viral infections in developed countries and the leading cause of congenital sensorineural hearing loss and psychomotor retardation. Babies of woman who experience a primary CMV infection while pregnant are at the greatest risk for long-term health issues. Although there is no cure for CMV, simple precautions such as limiting contact with small children and careful hand washing can decrease the likely hood of a primary maternal infection during pregnancy. Despite the prevalence of, and serious repercussions, from congenital CMV infection, there is still an alarming lack of awareness in the general public. In the United States, more children suffer from the permanent effects of congenital CMV than from Down syndrome, spina bifida and fetal alcohol syndrome—combined, and yet less than 15% adults have heard of it.

For More information about congenital CMV:

National CMV Foundation

CMV Action

Center for Disease Control and Prevention 

References

  1. Manicklal, S., et. al (2013) Clin. Microbio. Rev. 26, 86–102.
  2. Anonymous. (2008) Impact of expanded newborn screening—United States, 2006. MMWR Morb. Mortal. Wkly. Rep. 57, 1012–5.
  3. Swanson, D.O. and Schleiss, M.D. (2013) Pediatr. Clin. North Am. 60, 335–49.
  4. CDC Congenital CMV Infection Trends and Statistics; http://www.cdc.gov/cmv/trends-stats.html
  5. Boppana, S. et. al (2013) Clin. Infect. Dis. 57 Suppl 4, S178–81.
  6. Cannon, M.J. and Davis, K.F. (2012) Prev. Med. 54, 351–7.
  7. Kimberlin, D. et. al (2003) J. Pediatr. 143, 16–25.
  8. Oliver, S.E. et. al (2009) J. Clin. Virol. 46 Suppl 4, S22–6.

 

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Kelly Grooms

Scientific Communications Specialist at Promega Corporation
Kelly earned her B.S. in Genetics from Iowa State University in Ames, IA. Prior to coming to Promega, she worked for biotech companies in San Diego and Madison. Kelly lives just outside Madison with her husband, son and daughter. Kelly collects hobbies including jewelry artistry, reading, writing, photography and knitting. She would like to be an avid runner, as evidenced by her growing collection of running gear and her single half-marathon finishers t-shirt.

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