Tonsillitis is an infection of the tonsils that is usually caused by viruses like the common cold or bacteria like strep throat. The symptoms include a sore throat, pain when swallowing, fever, headache, tiredness, and swollen lymph nodes. While tonsillitis cannot always be prevented, reducing risk factors like hand washing and avoiding sharing food/drinks with sick people can help. Treatment depends on the cause - viral tonsillitis requires comfort measures while bacterial gets antibiotics. Repeated cases may require surgery to remove the tonsils (tonsillectomy).