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Column originally published Mar 31, 2020

Congenital CMV Infection Can Lead To Hearing Loss In Young Children

Question: Our three-year-old daughter was completely well until a year ago. She was a happy and talkative girl. Over a period of several weeks, we noticed that she didn’t respond when we spoke to her, although she still reacted to our dog’s barking. We finally took her to our doctor, and was referred to an audiologist. To our surprise, she had severe hearing lost in her left ear, although she could hear some in her right ear. It got worse after several months; she is now fitted with a hearing aid. This has improved her hearing, but she is not as bubbly as before. The audiologist suggested that she might have a viral infection before she was born. I have done some reading, and it terrifies me. I started working in a daycare when I was pregnant with her. Is there anyway to confirm this? We are considering having another child; can this happen to our next one also?


From your description, it is possible that your daughter’s hearing loss was due to congenital cytomegalovirus (CMV) infection. Let me explain this to you.

Scientists have discovered CMV more than 50 years ago. The name CMV comes from the observation that cells infected by this virus became much larger than normal uninfected cells.

Most of us got infected by CMV when we were very young, when we shared toys and saliva. We usually have mild cold-like symptoms. Once infected, the virus stays in our body, and we excrete new virus particles in our saliva and urine. Uninfected individuals can get CMV infection through exposure to saliva and urine of infected children.

Most adults were infected during childhood, therefore, immune to reinfection when exposed to CMV. A few adults didn’t get infected, and are still susceptible to the virus. If a pregnant susceptible woman gets infected with CMV during the first few weeks of pregnancy, the virus can infect the unborn foetus through the placenta. This is called congenital CMV infection.

Fortunately, the vast majority of these infected babies are normal at birth; they can have normal screening hearing test. Only five to 10% of these children show signs of infection at birth.

The most common complication of congenital CMV infection is sensorineural hearing loss. This virus can attack the cochlear, the organ in our inner ear that helps us to hear different sounds. This usually starts in the first few years of life, often more severe on one side, and can progress gradually for several years. Some children require hearing aids, while others may need cochlear implant: a small electronic gadget that bypasses the damaged cochlear and sends sound signals to the brain.

It is important to note that sensorineural hearing loss is different from the more common conductive hearing loss due to recurrent ear infections.

The only way to prove that a child has congenital CMV infection is to do blood and urine tests during the first few weeks of life. It is not possible to prove, at this stage, that your daughter’s hearing loss is due to this condition. Tests can show that she was infected with CMV, but cannot tell when it occurred.

If you were infected with CMV, either as a child, or when you were pregnant with your daughter, you are immune to the virus now and cannot have another infection. If you take medicine that suppresses your immune system, the CMV in your body can become re-activated at that time. Therefore, the chance of congenital CMV infection in your next child is very unlikely.

Ontario has initiated a screening test for congenital CMV infection recently. It uses the same blood sample taken for other newborn screening tests. Once a baby is identified, additional confirmation tests will be done. Babies with congenital CMV infection will have more frequent hearing tests to detect early hearing loss. Babies can be fitted with hearing aid in the first few months of life. This can prevent speech delay and impediment. This screening program is not available in other provinces yet.

I hope you have a better understanding of this condition. It is very unlikely that your next child will have congenital CMV infection.