Tonsils are circular areas of lymphoid tissue located on each side of the throat (pharynx). They are part of the body's immune system but often atrophy and shrink in adults. Tonsils can become infected from viruses or bacteria, resulting in tonsillitis.
Tonsillitis causes sore throat and red, swollen pus-coated tonsils with fever, headache, swollen glands in the jaw and neck, laryngitis (hoarseness) and difficulty swallowing.
Numerous viral infections can cause tonsillitis, including mononucleosis, Epstein-Barr, influenza, croup, laryngitis and herpes simplex, with widely varying times to onset; however, most viral tonsillitis clears in 2 to 5 days.
Bacterial tonsillitis, usually Streptococci A ("strep throat"), causes illness within 2 to 7 day, and most symptoms subside within about 5 days, but the tonsils may remain swollen for 3 to 4 weeks.
Both the viruses and bacteria that cause tonsillitis are spread by contact with body fluids, such as droplets from someone's cough or runny nose.
Once infected, you can spread infection to things you touch, so wash your hands often and cover your mouth when you cough.
Viral infections need only supportive treatment (fluids, acetaminophen) while bacterial infections require antibiotics.