Which virus is the most common cause of congenital hearing loss in infants?

• A. Herpes simplex virus
• B. Rubella
• C. Cytomegalovirus
• D. Toxoplasmosis

Answer: (C)

Cytomegalovirus is the most common infectious cause of congenital hearing loss in infants. When CMV crosses the placenta during pregnancy, it can damage the cochlea and auditory pathways, leading to sensorineural hearing loss that may be present at birth or appear later in childhood and can be progressive. This makes CMV a more frequent culprit for congenital deafness than rubella, toxoplasmosis, or herpes simplex virus, especially since rubella has become rare thanks to vaccination.

Newborns with congenital CMV may pass the initial hearing screen yet still develop hearing loss later, so CMV should be considered when there is unilateral or bilateral SNHL, or when other signs suggestive of CMV are present. Diagnosis is confirmed by detecting CMV DNA in urine or saliva within the first weeks of life. For symptomatic infants with CNS involvement, antiviral therapy with ganciclovir or valganciclovir can improve hearing and neurodevelopmental outcomes, though it does not eradicate the infection.