Strep throat is a contagious bacterial infection of the throat and tonsils caused by Group A Streptococcus (GAS). It spreads through respiratory droplets from an infected person’s cough or sneeze. Unlike a common sore throat caused by a virus, strep throat requires medical confirmation through testing and subsequent treatment with antibiotics. Identifying the cause is important because antibiotics are ineffective against viral infections.
The Hallmarks of Strep Throat
The onset of a strep infection is sudden, often beginning with a severe sore throat that develops rapidly over a few hours. This pain is accompanied by difficulty when swallowing. Upon physical examination, the tonsils and back of the throat often appear noticeably red and swollen.
A fever is a common sign of strep throat, often reaching 101°F (38.3°C) or higher, with the peak temperature sometimes occurring on the second day of the illness. A characteristic sign is the presence of white patches, streaks of pus, or visible redness on the swollen tonsils. Tiny, reddish spots called petechiae may also appear on the roof of the mouth. The lymph nodes in the front of the neck often become tender and swollen.
Children may experience less common symptoms such as headache, stomach pain, or nausea and vomiting, which can sometimes be the first signs of the infection.
Distinguishing Strep from Viral Sore Throats
A virus causes the majority of sore throats. The primary way to differentiate a bacterial strep infection from a viral illness is by looking for the absence of typical cold symptoms. Strep throat does not present with a cough, a runny or stuffy nose, or hoarseness. If a person has a sore throat along with any of these upper respiratory symptoms, the infection is likely viral.
Viral sore throats develop gradually, over two or three days, and are usually part of a broader cold or flu syndrome. The presence of conjunctivitis, commonly known as pink eye, also points toward a viral cause, as this symptom is not associated with strep throat. Recognizing these differentiating symptoms can help determine when professional testing is necessary. The ability to swallow without severe pain is another indicator that the infection may be less severe and viral.
Confirmation and Diagnosis
A diagnosis of strep throat cannot be made based on symptoms alone, as several viral illnesses can mimic the signs of a GAS infection. Laboratory testing is necessary to confirm the presence of Group A Streptococcus bacteria. This involves a healthcare provider performing a throat swab, which collects a sample from the back of the throat and tonsils.
The first test performed is often the Rapid Strep Test (RST), which provides results within minutes by detecting specific antigens. While the RST offers a quick answer, it has a lower sensitivity than a culture, meaning it may sometimes miss an infection. If the RST result is negative, especially in children and adolescents, the provider usually sends the original swab for a throat culture. This culture is considered the most accurate method, though results take 24 to 48 hours. Prompt diagnosis allows for the initiation of antibiotic treatment, which is important for reducing symptom duration and preventing complications such as rheumatic fever.