Mumps is a highly contagious viral infection that typically begins with flu-like symptoms, such as a fever, headache, muscle pain, and fatigue. The most recognizable sign is the painful swelling of the parotid glands (salivary glands located in the cheeks and jaw), a condition known as parotitis. While most cases resolve within a couple of weeks without lasting problems, the mumps virus can lead to serious complications in various organs, including the testes, pancreas, and brain. One less common, but concerning, long-term complication is permanent hearing loss.
Mumps and Sudden Hearing Loss
Yes, mumps can cause deafness, which is a form of sensorineural hearing loss. This complication is characterized by a sudden onset, often occurring during or shortly after the peak of the mumps infection.
The hearing loss is typically profound (severe or total) and, in the majority of cases, affects only one ear, making it unilateral. The impairment can manifest rapidly, sometimes starting within four to five days of the initial illness symptoms. Prior to widespread vaccination, mumps was considered the most common cause of acquired unilateral sudden deafness in children. The hearing loss may also be accompanied by vestibular symptoms like vertigo and dizziness, indicating the virus has affected the balance mechanisms in the inner ear.
How the Mumps Virus Damages Hearing
The hearing loss results from the virus directly infecting and damaging the delicate structures of the inner ear. The mumps virus travels through the bloodstream (viremia), allowing it to reach the inner ear, or labyrinth. Scientists propose the virus can cross the blood-labyrinth barrier to directly enter the fluid-filled spaces.
Once inside the cochlea, the spiral-shaped organ responsible for hearing, the virus triggers inflammation. This viral invasion and subsequent inflammatory reaction destroy the microscopic hair cells lining the cochlea. These hair cells translate sound vibrations into electrical signals that the brain interprets as sound. Because these specialized cells have a limited ability to regenerate, the resulting hearing loss is often permanent.
Risk Factors and Vaccination
The risk of developing mumps-related deafness is low, estimated to occur in approximately one out of every 20,000 cases in the pre-vaccination era. The vast majority of people infected with mumps will not experience this complication. Nevertheless, the possibility of permanent, unilateral deafness highlights the importance of preventing the infection.
The measles, mumps, and rubella (MMR) vaccine is the most effective method for preventing mumps and its complications. Vaccination dramatically reduced the incidence of mumps and, consequently, the number of deafness cases.
Two doses of the MMR vaccine provide a high level of protection, with a documented efficacy of around 88% against mumps. Routine immunization schedules recommend that children receive two doses. This practice protects the vaccinated individual and contributes to herd immunity, safeguarding infants and people with compromised immune systems who cannot receive the vaccine.