Is streptococcal pharyngitis (strep throat) contagious?

From the Guidelines

Strep throat is highly contagious and can spread through respiratory droplets, shared food and drinks, or contact with contaminated surfaces. The contagion period typically lasts until the infected person has been on antibiotics for 24-48 hours 1. According to the Infectious Diseases Society of America, accurate diagnosis of streptococcal pharyngitis followed by appropriate antimicrobial therapy is crucial for preventing the spread of the disease and reducing contagiousness 1.

Key Points to Consider

• Strep throat spreads through respiratory droplets when an infected person coughs or sneezes, but can also spread through shared food, drinks, or contact with surfaces contaminated with the Streptococcus bacteria 1.
• People with strep throat are typically contagious until they've been on antibiotics for 24-48 hours 1.
• The standard treatment is a 10-day course of antibiotics, commonly penicillin (such as amoxicillin) or azithromycin for those with penicillin allergies 1.
• Completing the entire antibiotic course is essential, even if symptoms improve, to prevent complications like rheumatic fever 1.

Prevention Measures

• Stay home from work or school while contagious to prevent the spread of the disease 1.
• Avoid sharing personal items, wash hands frequently, cover coughs and sneezes, and dispose of used tissues properly to reduce the risk of transmission 1.
• The bacteria can survive on surfaces for days and easily transfer between people in close contact, making it essential to maintain good hygiene practices 1.

From the Research

Contagiousness of Streptococcal Pharyngitis

• Streptococcal pharyngitis, also known as strep throat, is contagious and can be spread from person to person via respiratory droplets 2.
• The incubation period of streptococcal pharyngitis is short, typically ranging from 2 to 5 days 2.
• The disease is most common in school-aged children, with a peak at 7-8 years of age, and can occur in all ages, although it is rare in children under 3 years old and becomes less common in late adolescence and adulthood 2.
• Colonization with group A streptococcus (GAS) is higher in winter months, but colonization has not been shown to contribute to the spread of disease 2.
• Outbreaks of pharyngitis are common in low- and middle-income countries and in situations where crowding is common, such as schools 2.

Transmission and Prevention

• Close contacts of patients with invasive group A streptococcal infection are at risk of developing the disease, with 36% of close contacts who had exposure to the index patient for more than 24 hours/week testing positive for the same GAS clone 3.
• Targeted antibiotic prophylaxis and an educational campaign may be effective in preventing the spread of disease to close contacts 3.
• Rapid antigen testing and throat culture can be used to diagnose streptococcal pharyngitis, and antibiotic treatment can help prevent the spread of disease 4, 5, 6.
• Penicillin and amoxicillin are first-line antibiotics for the treatment of streptococcal pharyngitis, and patients allergic to penicillin can be treated with alternative antibiotics 4, 5, 6.