How long are you contagious with streptococcal (strep) pharyngitis?

Contagiousness Duration for Strep Throat

You are contagious with strep throat until you have completed 24 hours of appropriate antibiotic therapy. 1

Timeframe for Contagiousness

Without Treatment

• Untreated strep throat remains contagious for the entire duration of illness and potentially for weeks afterward as a carrier 1
• Asymptomatic carriers can harbor Group A Streptococcus for several months, though they are unlikely to spread the organism to close contacts 1

With Antibiotic Treatment

• The majority of individuals (96%) with pharyngeal carriage will be culture-negative 24 hours after starting appropriate antibiotic treatment 1
• Research confirms that approximately 83% of patients become culture-negative within the first 24 hours of antibiotic therapy 2
• However, 36% of patients may still have a positive throat culture the morning after initiating antibiotics, which is why the full 24-hour period is critical 2

Return to Work/School Guidelines

For General Population

• Children and adults should stay home from school or work until they have completed a full 24 hours of antibiotic therapy 2
• Even if patients feel clinically well by the morning after starting antibiotics, they should complete the full 24-hour period before returning to normal activities 2

For Healthcare Workers

• Healthcare workers with symptomatic strep pharyngitis must stay away from clinical work until at least 24 hours of appropriate therapy AND resolution of symptoms has occurred 1
• Asymptomatic healthcare workers who test positive should stay away from work until 24 hours of appropriate therapy 1
• A longer exclusion period may be required for healthcare workers with skin lesions or in outbreak situations 1

Important Clinical Considerations

Treatment Duration vs. Contagiousness

• While you are no longer contagious after 24 hours of antibiotics, the full 10-day course of penicillin or amoxicillin must be completed to maximize bacterial eradication and prevent acute rheumatic fever 3, 4
• Early treatment can reduce symptom duration to less than 24 hours in most cases and limit spread in the family and community 5

Common Pitfalls to Avoid

• Do not allow patients to return to school, work, or daycare before completing 24 hours of antibiotics, even if they feel better 2
• Do not confuse the 24-hour contagiousness window with the 10-day treatment duration—both are important for different reasons 3, 2
• Do not assume asymptomatic household contacts need treatment, as routine prophylaxis is not recommended and up to one-third may be carriers without clinical disease 6

When Contacts Should Be Tested

• Household contacts should only be tested and treated if they develop symptoms consistent with strep pharyngitis 6
• Routine testing or empiric treatment of asymptomatic contacts is not recommended, as penicillin prophylaxis has not been shown to reduce the incidence of subsequent strep pharyngitis in household contacts 6