Four-year-old Jakob Boot loves to play ball with his older brother, Niko. In fact, he likes doing just about everything his brother does. Little brothers often have a hard time keeping up but Jakob faces challenges bigger than most. Jakob was born with congenital cytomegalovirus (CMV), an infection which caused him to become profoundly hard of hearing in both ears. Unfortunately, Jakob’s situation is not unusual. Though it garners little attention in the lay and scientific press, congenital CMV is the most common cause of sensorineural hearing loss in children in the United States and is a leading cause of vision loss and mental retardation.
Most CMV infections are asymptomatic or cause only mild flu-like symptoms, but when a pregnant woman is infected and passes the infection to her unborn baby, there can be serious consequences. Each year in the U.S., an estimated 40,000 babies are born with congenital CMV infection, causing an estimated 400 deaths and leaving approximately 8,000 children with permanent disabilities, the most frequent of which is sensorineural hearing loss. According to some estimates, 20 to 30 percent of all sensorineural hearing loss is caused by CMV. The disabilities caused by congenital CMV, particularly hearing loss, often have a delayed onset and may grow more severe with time. The direct annual economic costs of caring for these children are estimated at $1 billion to $2 billion, though no amount of money compares to the suffering of the families affected by the disease. More children are adversely affected by congenital CMV disease than by some childhood diseases or syndromes which are widely known, such as Down syndrome or fetal alcohol syndrome.
Transmission and Prevention
CMV is spread through close contact with body fluids, especially urine and saliva. Transmission can occur via contaminated hands (which then touch the mouth or eyes), through sexual contact, breastfeeding, blood transfusions and organ transplantation. CMV is not transmitted through the air. Young children are more likely to be a source of CMV than older children or adults. For a pregnant woman, the most likely source of infection is contact with the urine or saliva of young children, especially her own children.
Testing Women for CMV
A CMV IgG antibody test reliably indicates whether a woman has been exposed to CMV but it does not indicate whether she was infected prior to or during pregnancy. If a woman was infected prior to pregnancy, she is much less likely to have a baby with congenital CMV disease. If she was infected during pregnancy, her fetus has a one in three chance of becoming infected, and if infected, a one in five chance of suffering permanent disabilities. Additional laboratory tests, such as an ultrasound or detection of CMV in amniotic fluid, can sometimes identify babies who will have CMV-related disabilities. Anti-CMV drug treatments have questionable efficacy and are too toxic to be widely recommended. For these reasons, it is not clear whether CMV testing during pregnancy is warranted. On the other hand, CMV testing prior to pregnancy may prove to be a useful prevention tool, since a woman who has not been exposed to CMV prior to conception will know that she should take extra precautions to prevent infection during her pregnancy.
Newborn Screening
Diagnosis of congenital CMV requires detection of the virus or viral DNA in a baby’s bodily fluids within two to three weeks after birth. Diagnosis is often missed because infected infants are usually asymptomatic at birth or have non-specific symptoms. As a result, CMV testing may not be done.
Infants are not routinely screened for CMV infection at birth. Universal screening would detect children at high risk for delayed hearing loss. Despite testing normally at their newborn hearing screening, CMV-infected children can go on to develop hearing deficits over months and even years. If they test CMV-positive at birth, they should have regular hearing examinations, which would help detect hearing loss early and allow early interventions to aid learning and language development.
Perhaps no single cause of hearing loss in the U.S. currently provides greater opportunity for improved outcomes in more children than congenital CMV. Future research should focus on vaccine development, effective hand-hygiene interventions for preventing CMV infection among pregnant women and the feasibility and cost-benefit of universal newborn screening. Advances in these areas will allow more children to grow up without the struggles that little Jakob faces.
For further information, visit www.cdc.gov/cmv.
