Tonsillitis is inflammation of the tonsils, typically of rapid onset. It is a type of pharyngitis. Symptoms may include sore throat, fever, enlargement of the tonsils, trouble swallowing, and large lymph nodes around the neck. Complications include peritonsillar abscess. Tonsillitis is most commonly caused by a viral infection, with about 5% to 40% of cases caused by a bacterial infection.[4][5] When caused by the bacterium group A streptococcus, it is referred to as strep throat. Rarely bacteria such as Neisseria gonorrhoeae, Corynebacterium diphtheriae, or Haemophilus influenzae may be the cause. Typically the infection is spread between people through the air.