Several viruses can cause sudden hearing loss, but the herpes virus family is considered the most likely culprit. Herpes simplex virus (HSV), varicella-zoster virus (the virus behind chickenpox and shingles), cytomegalovirus, and Epstein-Barr virus are the most frequently implicated. Mumps, measles, rubella, HIV, hepatitis viruses, and more recently SARS-CoV-2 have also been linked to sudden hearing loss.
Sudden sensorineural hearing loss (SSNHL) is defined as a drop of 30 decibels or more across at least three sound frequencies within 72 hours. It affects roughly 27 out of every 100,000 people in the United States each year, and in many cases, the exact cause is never confirmed. Viral infection is one of the leading theories.
Why Herpes Viruses Top the List
The herpes virus family gets the most attention because nearly everyone carries at least one of these viruses. About 91% of adults test positive for HSV-1, 90% for varicella-zoster, 90% for Epstein-Barr virus, 95% for human herpesvirus 6, and 70% for cytomegalovirus. These viruses share an important trait: after the initial infection, they go dormant in nerve tissue and can reactivate later when the immune system is weakened.
Varicella-zoster virus offers the clearest example of how this works. After causing chickenpox in childhood, the virus hides in nerve clusters near the inner ear, including the spiral ganglia and vestibular ganglia. When it reactivates, it can trigger Ramsay Hunt syndrome, a condition that causes facial paralysis and sudden hearing loss on one side. This reactivation pattern explains why sudden hearing loss sometimes appears in people who haven’t had a recent illness. The virus was already there, waiting.
In one study, 81% of patients with sudden hearing loss who had high levels of HSV-1 antibodies improved after antiviral treatment alone.
Mumps and Other Childhood Viruses
Mumps has a well-established connection to sudden deafness, though estimates of how often it happens vary widely. Conservative figures suggest 0.005% to 0.3% of people infected with mumps experience sudden hearing loss. Other research puts the rate as high as 4% in adult mumps patients. Measles and rubella have also been linked to hearing damage, though widespread vaccination has made these causes far less common in countries with high immunization rates.
COVID-19 and Hearing Loss
SARS-CoV-2 has emerged as a potential cause of sudden hearing loss, though the evidence is still building and largely based on case reports and smaller studies rather than large-scale trials.
The virus has several plausible routes to damage hearing. The inner ear’s key structures, including the organ of Corti (which converts sound into nerve signals), the spiral ganglion neurons, and the stria vascularis (which maintains the chemical balance the ear needs to function), all have the ACE2 receptors that SARS-CoV-2 uses to enter cells. Once inside, the virus triggers a flood of inflammatory molecules that can increase oxidative damage to delicate hearing structures.
COVID-19 also promotes abnormal blood clotting. The virus can infect the lining of blood vessels feeding the inner ear, causing inflammation, platelet activation, and small clots that starve hearing structures of oxygen. It can even bind to red blood cells directly, reducing their ability to carry oxygen. A third pathway involves the virus crossing into the brain and inflaming the auditory cortex in the temporal lobe, which processes sound.
Adding another layer of complexity, some medications used to treat COVID-19 early in the pandemic, including hydroxychloroquine and certain antivirals, are themselves known to damage hearing.
How Viruses Damage the Inner Ear
Viruses cause hearing loss through two main mechanisms. The more common route is indirect: the virus triggers an immune response, and the resulting inflammatory chemicals enter the cochlea (the snail-shaped hearing organ) through membranes called the round or oval window. This inflammation disrupts the cochlea’s finely tuned environment and damages the hair cells that detect sound.
Less commonly, a virus directly invades the cochlea itself. This can destroy hair cells and nerve fibers outright. Unlike many cells in the body, the hair cells inside the human cochlea do not regenerate. Once they’re gone, the hearing loss they supported is permanent.
Why the Cause Is Often Unknown
In most cases of sudden hearing loss, doctors cannot pinpoint the exact virus responsible. By the time someone notices the hearing drop and gets tested, the acute viral infection may have already passed, leaving no detectable trace in standard blood work. MRI scans sometimes show inflammation or enhancement in the inner ear, suggesting an active inflammatory process, but this doesn’t identify which virus started it.
The distinction between viral and vascular causes (where a blood flow disruption damages the ear, similar to a mini-stroke) matters for treatment but is difficult to make in a living patient. Post-mortem studies have found that vascular hearing loss tends to produce scarring in the base of the cochlea and significant nerve cell loss, while cases classified as idiopathic (cause unknown, but often suspected viral) typically show less structural damage and more normal nerve cell counts. In practice, though, these are findings from tissue analysis, not tests your doctor can run in the office.
Treatment Timing Matters More Than the Cause
Regardless of which virus may be involved, the treatment approach is the same: steroids to reduce inflammation, started as quickly as possible. The standard first-line treatment is oral corticosteroids for one to two weeks, followed by a gradual taper. If oral steroids don’t work, steroid injections through the eardrum directly into the middle ear are used as a backup, typically given every three to seven days over three to four sessions.
The window for effective treatment is narrow. Patients who begin treatment within the first week of symptom onset have an 87% recovery rate. That drops to 52% if treatment starts in the second week, and falls below 10% if more than three months pass. Guidelines recommend starting steroid therapy within two weeks at the latest, but sooner is clearly better.
Recovery Odds
The good news is that sudden hearing loss has a relatively high rate of spontaneous recovery, estimated at around 60% across pooled studies. This means that roughly three in five people regain some or all of their hearing even without treatment. However, that still leaves a substantial number who don’t recover on their own, which is why early treatment remains important. There’s currently no reliable way to predict at the outset who will recover spontaneously and who won’t.
Several factors tend to predict worse outcomes: older age, more severe initial hearing loss, dizziness or vertigo alongside the hearing drop, and delays in seeking treatment. Hearing loss that affects lower frequencies tends to recover better than loss concentrated in higher frequencies.