6. Sore Throat
The most common cause of sore throat in flu patients is tonsillitis, or the inflammation of the tonsils, a pair of soft tissue masses towards the back of the throat. This is because the tonsils serve a similar role to that of the lymph nodes by assisting the body’s immune system in filtering harmful substances such as toxins and viruses from the plasma. The swelling of the tonsils is accompanied by a sharp pain when swallowing or coughing, making it difficult for patients to eat or even speak.