It is already well-known that hearing loss can occur from congenital infections such as rubella, herpes simplex and syphilis. But it is also evident for newborns infected by Zika virus.
In total, four out of 60 (5.8%) tested infants in a conducted study showed signs of hearing loss during the period of time the study was carried out. Normally, only 1 pr. 1000 newborn infants suffer from hearing loss. Therefore, Zika virus increases the risk of hearing loss with about sixty times compared to normal standards.
In light of the strong correlation between Zika virus and risks of hearing loss, all infants born to women with diagnosed Zika virus-infection should have tested, whether their hearing abilities have been affected by the mother’s infection.
The researchers tested the infants´ hearing threshold as a method to predict whether the infants hearing abilities were damaged by the Zika virus-infection. In the study, hearing loss was considered, if the infants´ hearing threshold was more than 25 decibels below normal hearing level. The study contained two tests with an interval of one month. If the infant´s test results in both cases were atypical, hearing loss was diagnosed.
About the study
The study was carried out by Mariana C. Leal, professor of otolaryngology from the Federal University of Pernambuco in Brazil. The study took place in the period between November 2015 and May 2016, and included 70 infants aged between 0 and 10 months with a positive diagnosis of Zika virus and microcephaly. Microcephaly is a condition, where the brain does not develop properly, resulting in a physical smaller head when an infant is born.