Sore Throat: Virus or Strep?

Are you wondering if your sore throat requires antibiotics? Strep throat, named for the Streptococcus bacterium that causes the condition, is a particularly severe form of sore throat that is best treated with antibiotics. Strep throat can strike both children and adults, but only about 5%-10% of sore throats are caused by a bacterial infection. Most sore throats are caused by viral illnesses and are not responsive to treatment with antibiotics.

What are the symptoms of strep vs. a viral infection?

A true streptococcal infection of the throat often leads to excruciating throat pain accompanied by difficulty swallowing and even speaking. Fever may be present, and the tonsils are often covered with a whitish layer of pus. Cough and runny nose are not commonly related to strep throat, but it is possible to have a streptococcal infection along with a viral upper respiratory infection and symptoms of a cold. The bacterial infection may result in enlarged, tender lymph nodes in the neck. Children may have an accompanying rash; a streptococcus infection along with a rash is commonly termed scarlet fever.

It's important to distinguish between bacterial and viral causes of sore throats. Your doctor can perform a rapid strep test that generally indicates within a few minutes whether Streptococci are present in the inflamed area. Alternatively, a culture sample can be taken from the throat area with a cotton swab and evaluated in the laboratory for bacterial growth. The culture usually takes about 24 hours before Streptococci can be identified.

What are complications of strep throat?

Untreated Streptococcus infection of the throat can lead to rheumatic fever, a disease that damages the heart valves and affects the joints. A kidney inflammation known as a glomerulonephritis, which results in impaired functioning of the kidney, can also occur if streptococcal infections are not adequately treated. Due to the availability of antibiotic treatment, both of these conditions are rarely seen today.

If you suspect that you or your child has strep throat, visit a clinic to be tested. Do not begin taking any antibiotics until a culture or strep test has been performed, since even one dose of antibiotic can influence the accuracy of the testing. If a swollen throat is causing breathing difficulties or severe problems with swallowing, seek immediate medical assistance.

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Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.