CDC States Congenital Zika Infection May Cause Hearing Loss

It’s been confirmed that congenital infection with the Zika virus causes neurological complications, such as microcephaly, to developing fetuses. Now, a Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report states that congenital Zika infection may cause hearing loss.

Researchers from the Hospital Agamenon Magalhaes in Brazil screened 70 infants between 0 and 10 months who were diagnosed with microcephaly and had lab evidence of Zika infection, between November 2015 and May 2016. Of the pool of 70, five of these infants—who also presented with severe microcephaly—were found to have sensorineural hearing loss, which is characterized by damage to the inner ear or hearing nerve, according to the CDC. The severity and laterality of the Zika-related hearing loss varied among the infants, which is consistent with hearing loss associated with other congenital viral infections.

One of the infants was found to have bilateral profound sensorineural hearing loss, but was treated with amikacin, an ototoxic antibiotic, before testing. Dismissing this case from the percentage of those diagnosed with sensorineural hearing loss broight the prevalence down to 5.8%. According to the study authors, “This proportion, although lower than the 9% reported from a small sample of newborns with microcephaly associated with presumed Zika-virus infection tested by otoacoustic emissions, is within the range (6%—65%) reported for other congeni­tal viral infections.” Hearing loss caused by congenital infections is usually due to damage to the cochlea; however, the study researchers stated they cannot rule out damage to other areas of the ear as a cause of hearing loss in Zika-related congenital hearing loss.

Forty-one of 63 mothers of infants in the study were found to have experienced rashes in the first trimester of pregnancy, due to Zika infection. Of the mothers whose infants were diagnosed with sensorineural hearing loss, four reported rashes in the first 3 months of pregnancy. The researchers report that the timing of a Zika-related rash did not differ between those mothers whose infants developed this complication; however, they also reported that there was no significance between timing of rash during pregnancy and the degree of microcephaly. Furthermore, the researchers state that the prevalence of worsening hearing loss due to congenital Zika infection is still unknown.

Auditory testing in all infants born to mothers infected with the Zika virus during pregnancy, regardless of evidence of congenital infection, is recommended. Because auditory impairment in these populations may be delayed or may worsen, researchers also recommend follow-up testing.