The Zika virus that made headlines last year has already slowed down. However, it is only now that researchers are finding out about the negative consequences that the virus can cause on people's hearing.
When it comes to its effects on the body and mode of transmission, the Zika virus shares similar properties with the West Nile virus and dengue fever. All three are borne through the bites of mosquitoes, and anyone, regardless of age or gender, can be affected by the disease (though those with weaker immune systems like babies and the elderly are especially vulnerable).
Despite its similarities, at least 80% of the cases of people afflicted with the Zika virus are asymptomatic. The remaining 20% exhibit visible symptoms such as high fever, joint and muscle pain, headaches, rash, light sensitivity, and conjunctivitis. Most patients can recover in about a week or two.
It doesn't really sound that bad on paper. But one out of five patients who were afflicted with the virus can experience lingering effects. For babies who were exposed in utero, it can be more damaging since they will be high at risk for brain damage and other birth defects.
On Hearing Loss
Dr. Viviane Boaventura, a Brazil-based researcher and an ENT (ear, nose, and throat) physician, is currently focused on a group of patients who reported a different set of symptoms that weren't seen in most Zika virus cases: tinnitus, vertigo, and hearing loss. In fact, even though most of the primary symptoms were gone, the hearing-related ones still remain, even continuing months after the initial exposure to the virus.
At this point, even though most of the patients have fully recovered, the long-term effects are still not clear. Dr. Boaventura mentioned in an interview that she is still not sure if the damage is reversible or will stay permanent.
Dr. Boaventura isn't the only researcher leading the study into hearing loss caused by the Zika virus. The American Academy of Audiology is focused on younger Zika patients with a particular emphasis on newborns whose mothers were afflicted by the virus early on in their pregnancy.
Due to the fact that these newborns are at higher risk of developing microcephaly (condition wherein the child is born with an abnormally small cranium), they are also at high risk for hearing loss too.
As explained by pediatric neurologist Dr. Sumit Parikh at the Cleveland Clinic Children's Hospital, stopping the brain's growth will also stop the skull from growing further.
The small head size isn't actually the problem- not all microcephaly cases come with brain damage. However, the Zika virus can cause a very severe and extreme form of microcephaly wherein the brain is not only stopped from growing, but it also becomes smooth too, with the normal ridges and folds not developing. Without these folds and ridges, there would be less surface area on the brain for neurons to develop.
According to Dr. Ganeshwaran Mochida of the Boston Children's Hospital, the most critical cases are babies with mothers who exhibited symptoms during the second to fourth month of pregnancy. This is the period wherein most neurons are formed, and it will be hard for the baby's brain to "catch up" if there are not enough neurons made during this point in the pregnancy.
Since Zika is a relatively new affliction (with the first cases having only been reported in 2013), the research regarding its connection with hearing loss is still at its beginning stages. At this point, scientists and doctors can only theorize. Some attribute it to the lack of neurons, while others to the calcifications on the babies' brains. But whatever it is, the American Academy of Audiology points out that infants who have the virus (borne through their infected mothers) might have absent or damaged hearing at birth, thereby necessitating the need for newborn hearing screenings.
The Zika virus can be transmitted through the bites of infected Aedes mosquitoes or through sexual contact with individuals who have contracted the virus. Those high at risk for Zika (elderly, pregnant women, women who are planning to get pregnant) should avoid going to areas where there are rampant Zika cases (e.g. South America, South Florida, New Guinea). Sexual contact with people who have been to these places should be avoided too.