Tonsillitis is inflammation of the tonsils, two oval-shaped pads of tissue at the back of the throat — one tonsil on each side. Signs and symptoms of tonsillitis include swollen tonsils, sore throat, difficulty swallowing and tender lymph nodes on the sides of the neck. Tonsillitis is usually caused by a viral infection but can be from a bacterial infection. most common in children ages 5 to 15. SYMPTOMS A sore throat with fever A sore throat that doesn't go away within 24 to 48 hours Painful or difficult swallowing Extreme weakness, fatigue .