Cytomegalovirus (CMV) is the most common cause of non-genetic sensorineural hearing loss (SNHL) in children. CMV is part of the herpes simplex family of DNA viruses. Once infected it stays latent in the body for a long time. When reactivation occurs CMV can cause symptoms in immunocompromised patients and infect others.It is present in nearly every person but usually only causes symptoms in babies, smaller children and immunocompromised adults. It is often acquired in utero. The estimation is that 1% of all newborns in the USA are infected with CMV. Of the babies with congenital CMV about 50% are infected when the mother develops a primary (for the first time) infection.
CMV form part of a group of infections known to be harmful and cause abnormal development (teratogenic) in babies. This group is called STRORCH, an acronym for syphilis, toxoplasmosis, rubella (German measles), cytomegalovirus and herpes. The birth defects of these infections are more or less the same. Besides brain damage, visual problems, seizures and retarded growth it also causes SNHL.
Of the children born with symptomatic CMV, 14% will develop mild hearing loss and 5% severe SNHL in both ears. The mortality rate in symptomatic CMV newborns is 5% and the survivors usually have permanent disabilities. Hearing loss can also occur in asymptomatic children and sometimes the hearing loss may only manifest months or years after the infection. The average age of diagnosis of SNHL is between 2 and 3 years of age. Continued screening for hearing loss is therefore important. The exact mechanism of how CMV causes hearing loss is not known. The hearing loss is usually more severe, progressive and bilateral in the children with symptomatic CMV.
Early treatment with anti-virus medication may prevent and even improve hearing loss. In others, hearing aids or cochlear implantation (CI) may be the only solution. Treatment in pregnancy is still controversial. The best is to avoid contact with infected persons, washing of hands and avoiding contact of small children’s urine and saliva. Unfortunately there is currently no effective vaccine available. If you think your baby or child has hearing loss don’t delay, have it tested as soon as possible.