Risk Factors and Causes

The cause of tonsillitis is most often a viral infection, but bacterial infections are possible as well. Tonsillitis caused by a virus is more common in younger children, while bacterial tonsillitis is more common in children over the age of five.

One of the bacterial infections you've probably heard about most in connection with tonsillitis is strep throat, caused by group A Streptococcus bacteria. Learn more about Strep Throat.