Influenza, or “the flu,” is a contagious respiratory illness caused by several different but related viruses. While the flu can spread year-round, the fall and winter “flu season” is when it’s most prevalent.  
The most common symptoms include: 

• Fever 
• Cough 
• Sore throat 
• Runny or stuffy nose 
• Muscle or body aches 
• Headaches 
• Fatigue 

Flu viruses infect the nose and throat, which are both closely connected to your inner-ear systems. Head congestion, or a stuffy nose, and inflammation can cause fluid buildup in your sinuses and ears, which makes sounds seem muffled. While sounds will still be clear, you may find yourself needing to turn up the volume. 
This is how the flu can cause conductive hearing loss, which, in this case, is temporary and should clear up with the related flu symptoms. 
However, in some cases congestion can lead to more serious infections.  

Potential complications of the flu 

Most hearing loss associated with the flu is temporary, but in rare instances, more serious complications from the flu can lead to permanent hearing damage. 

Otitis media (middle ear infection) 

A viral or bacterial infection of the middle ear can put pressure on the eardrum, leading to muffled sounds and hearing loss. This is usually a complication of flu- or cold-related congestion and swelling of the nasal passage and throat, which connect to the inner ear. 
While more common in children, it is possible for adults to contract an ear infection. Symptoms include ear pain (particularly when lying down), fluid coming from the ear, and hearing loss. If the ear pain is severe or symptoms last more than a day, contact your doctor.

Otitis interna (inner ear infection) 

A middle ear infection can migrate to the inner ear, resulting in further hearing loss and even loss of balance. There are different types of inner ear infections based on which particular organ is infected, but they all show the same symptoms: problems balancing, vertigo, dizziness, nausea and vomiting, headaches, earaches, and hearing issues. 
If untreated, an inner ear infection can lead to permanent hearing loss and long-term problems with balance. Check with your doctor if you have any of the symptoms above.

Meningitis 

Meningitis is a swelling of the protective membranes covering key parts of the nervous system, including the brain. The influenza virus can cause viral meningitis, which is less severe than bacterial meningitis, but it is also more common.
Severe cases of both types of meningitis can lead to hearing loss due to damage to the inner ear cells and even to the nerves that carry sound signals to the brain. This is more common with bacterial meningitis.
If you’re experiencing fever, headache, stiffness in your neck, nausea, confusion, or find your eyes more sensitive to light, consult your doctor about whether you should get checked for meningitis.

Tinnitus 

Tinnitus often presents as a ringing, buzzing, roaring, whistling or similar persistent noise in the ear. While the exact cause of tinnitus is unknown, there is some evidence that one potential factor could be fluid buildup in the inner ear, infection, and inflammation related to the flu or a common cold.

Preventing hearing loss during flu season 

The best way to avoid these complications is at the source — protecting yourself from getting the flu in the first place. The annual flu vaccine lowers your chances of both getting sick and getting seriously sick. In other words, you’re less likely to catch the flu, and even if you do, it won’t be as severe. 
If you do get sick this winter, over-the-counter decongestants can help relieve some of the symptoms that might develop into more serious complications. Drink plenty of fluids, get plenty of rest, and try some nutrient-rich holiday recipes. 

Sources 

https://www.mayoclinic.org/diseases-conditions/ear-infections/symptoms-causes/syc-20351616 
https://my.clevelandclinic.org/health/diseases/24240-inner-ear-infection-otitis-interna 
https://www.mayoclinic.org/diseases-conditions/meningitis/symptoms-causes/syc-20350508 
https://www.verywellhealth.com/long-term-effects-meningitis-5120622 
https://www.cdc.gov/meningitis/about/index.html#cdc_disease_basics_symptoms-symptoms 
https://www.healthline.com/health/tinnitus-after-cold