Bacterial pharyngitis, commonly known as strep throat, is a highly contagious infection of the throat and tonsils. It is caused by a specific microbe that spreads easily from person to person. Untreated infections pose a risk of serious complications.
Identifying the Causative Agent
The majority of bacterial pharyngitis cases are caused by the bacterium Streptococcus pyogenes, also known as Group A Streptococcus (GAS). GAS is a gram-positive bacterium that commonly resides in the throat and on the skin. This bacterial cause sets strep throat apart from the more common viral pharyngitis, which accounts for the majority of sore throats.
Viral pharyngitis does not respond to antibiotics, but a confirmed GAS infection requires antibiotic treatment. Antibiotic therapy is necessary to alleviate symptoms and prevent serious complications, such as rheumatic fever.
Mechanisms of Transmission
The bacteria move from an infected person to a susceptible person primarily through direct contact with respiratory secretions. When an infected individual coughs or sneezes, tiny droplets containing Streptococcus pyogenes are launched into the air. Transmission occurs when a healthy person inhales these droplets or transfers them to their mouth, nose, or eyes.
Close personal contact, such as kissing, can also facilitate the direct transfer of nasal and throat discharges. Indirect transmission is possible, though less common, when a person touches a contaminated surface, known as a fomite. Examples include doorknobs, shared utensils, or toys, followed by touching the face. The risk of spreading the bacteria is greatest when the infected individual is symptomatic.
Duration of Contagiousness
A person with bacterial pharyngitis is highly contagious from the onset of symptoms and remains so until the bacteria are effectively eliminated. For individuals who do not receive appropriate antibiotic treatment, the contagious period can last for two to three weeks, even if symptoms begin to improve.
Starting appropriate antibiotic therapy dramatically shortens the period of infectivity. The widely accepted “24-hour rule” indicates that a person is no longer considered contagious after completing at least 24 hours of antibiotics. This rapid reduction in bacterial load allows individuals to safely return to school or daycare. While contagiousness ends after 24 hours, the full course of antibiotics must be completed as prescribed to ensure complete bacterial eradication and prevent long-term complications.
Preventing Spread and Recurrence
Prevention strategies focus on limiting the transmission of respiratory secretions and reducing the risk of reinfection. Consistent and thorough hand hygiene, using soap and water for at least 20 seconds, is the most effective measure to interrupt the spread of the bacteria. Infected individuals should cover their mouth and nose completely when coughing or sneezing, ideally using a tissue that is immediately disposed of.
To prevent indirect transmission, frequently disinfect high-touch surfaces in the home, such as countertops, light switches, and electronic devices. Individuals must avoid sharing food, drinks, and eating utensils with anyone who is sick. A specific step to prevent recurrence is replacing the toothbrush within 24 hours of starting antibiotic treatment, as Streptococcus pyogenes can linger on the bristles and potentially lead to reinfection.