Strep throat occurs most commonly from October to April, often in children 5 to 10 years old. It can also occur in adults. The infection is spread by person-to-person contact with nasal secretions or saliva, often among family or household members.

Streptococci are the most common bacterial cause of pharyngitis. The organism may be present in the throat of people without causing a sore throat. This is referred to as colonization.

Small children frequently have no symptoms or symptoms too mild for diagnosis. Even though the sore throat usually gets better on its own, people who have strep throat should take antibiotics to prevent some of the more serious complications of this infection, particularly acute rheumatic fever.