Strep Throat Diagnosis

Viral or Bacterial?

When diagnosing a patient with a particular illness, providers will look for either viral or bacterial infections, as both types of illnesses can cause sore throats. While viruses are the most common cause of sore throats in people of all ages, strep throat is caused by bacteria, Streptococcus pyogenes (also known as group A streptococcus). Unlike viruses, bacteria can survive outside a living host. This means that strep bacteria can live and reproduce on objects and surfaces, increasing the risk of infection by touching or sharing objects or spaces with infected people. Overall, strep throat accounts for a very small portion of diagnosed sore throats. It’s estimated that group A strep, the most common bacterial cause of strep throat, causes 20–30% of cases of sore throats in children, and about 5–15% of sore throats in adults. Symptoms of a viral infection causing a sore throat include a cough, rhinorrhea (runny nose), hoarseness, ulcers in the mouth, and conjunctivitis (“pink eye”). Because antibiotics are only meant to treat bacterial infections, they are ineffective against viral infections.

Strep Throat Test

Your medical history, as well as a clinical examination, can be used to diagnose viral pharyngitis when viral symptoms are obvious. If a viral infection has been ruled out as a cause for your sore throat, a strep throat test administered by a provider will determine if your symptoms are caused by strep bacteria. The preliminary test, a rapid antigen test^[7], is quick. In performing this test, a provider swabs the throat to test for the presence of bacteria, which can be detected within minutes. If this test returns negative, a provider may proceed with a throat culture to confirm the presence of bacteria. A throat culture involves a provider rubbing a sterile swab over the back of the throat and tonsils to obtain a secretion sample. This sample is then sent to a laboratory, which creates a culture of it. It can take up to two days for the results of the culture to identify the presence of bacteria. While throat cultures can be uncomfortable, sometimes leading to gagging or watery eyes, they are generally quick, and discomfort subsides almost immediately. Let your healthcare provider know if you have a sensitive gag reflex before a throat culture is taken so that he or she can take the necessary steps to make you as comfortable as possible.

When should I see my healthcare provider?

You should seek immediate care if your child shows severe symptoms, such as difficulty breathing or swallowing or unusual drooling (which may indicate an inability to swallow). Even a slight increase in body temperature can be dangerous, as fevers are often more concerning in children than in adults. If you’re an adult, go to the provider if you have a sore throat accompanied by any of the following problems:

• A sore throat that is severe or lasts longer than a week
• Frequently recurring sore throat
• Difficulty swallowing
• Difficulty breathing
• Difficulty opening your mouth
• Joint pain
• Earache
• Rash
• Fever higher than 101°F (38.3°C)
• Blood or saliva in your phlegm
• A lump in your neck
• Hoarseness lasting more than two weeks
• Swelling in your neck or face

Other causes of a sore throat:

Not all sore throats are caused by strep bacteria. Sometimes, sore throats can be caused by viral infections. Some of these include:

• The common cold^[8]: a viral infection of the respiratory system (your nose and throat) causing congestion, cough, and fatigue
• The flu (influenza^[9]): similar to the common cold, but generally comes on more quickly and causes fever, muscle aches, and chills
• Mono (mononucleosis^[10], the “kissing disease”): less symptomatic in young children, an infection causing fatigue, sore throat, fever, and swollen lymph nodes that lasts roughly 4–6 weeks
• Measles^[11]: a childhood infection characterized by widespread rash
• Chickenpox^[12]: an infection causing an itchy rash with fluid-filled blisters
• Croup^[13]: an illness common in children that causes dry, harsh, barking cough
• Whooping cough (pertussis^[14]): a highly contagious respiratory infection

A sore throat can also develop because of external or physical causes. These include:

• Allergies
• Dryness
• Irritants (such as air pollution, tobacco smoke, alcohol, or spicy foods)
• Muscle strain (from yelling, singing, or talking loudly)
• Gastroesophageal reflux disease (GERD^[15])
• Immunodeficiency conditions like HIV^[16]
• Tumors

Sometimes, a sore throat can be treated by resting, drinking warm liquids, and avoiding irritants. However, if you experience persistent symptoms or believe you have an infection, go to your provider for diagnosis and treatment. Generally, you should go to the provider if you have a sore throat lasting longer than two days. You should also alert your provider if you have a sore throat accompanied by swollen lymph nodes or a rash, fever, or difficulty breathing or swallowing.