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STREP THROAT: Are you sure you have a Strep A Infection?

This article aims to give a general, but still in-depth, insight into Strep throat, Streptococcus A and Strep A Test. The article is based on a scientific and medical literature review, including statistical data and references for further reading.

Introduction

Strep throat is an infection of the Throat and tonsils caused by the bacteria Streptococcus pyogenes – a Group A Streptococcus (GAS), known as Strep A. Bacteria is also responsible for other conditions such as pneumonia, impetigo, cellulitis, rheumatic fever.

Infection is most common in children aged 5-15 but can affect people of any age. Early diagnosis and treatment are crucial. Viruses cause most sore throats, but strep throat needs to be treated with antibiotics to prevent complications.

There are two common types of tests to diagnose strep throat: the Rapid Strep A Test, which provides results in 10-20 minutes, and the throat culture, which is more accurate but takes 18-48 hours to get the result.

Keywords: Strep A, Strep Throat, Throat Infection, Streptococcus A, Group A Streptococcus, Strep A Test, Throat Culture.

What is Strep A?

Strep A, also known as Group A Streptococcus (GAS), is a spherical-shaped bacteria (coccus, pl. cocci) with a thick wall, and it is not able to move (non-motile).

Streptococcus pyogenes typically infect the throat and the skin. Bacteria are not part of the normal microbiota1 and are considered a major human-specific bacterial pathogen2.

Infection with Streptococcus A can cause various health problems, from milder forms, such as pharyngitis and impetigo, to more severe complications, such as pneumonia, scarlet fever, sepsis, and streptococcal toxic shock.3 Streptococcus A is also the most common cause of angina.

Image of Streptococcu pyogenes bacteria.
Streptococcus pyogenes

Other names for Strep A: Streptococcus A, Group A beta-hemolytic Streptococcus pyogenes, Group A Streptococcus (GAS), Streptococcus pyogenes.

What is Strep Throat?

Strep Throat is the other name for a throat infection caused by Strep A bacteria. It is also known as Streptococcal pharyngitis (Streptococcal Sore Throat).

Pharyngitis means Sore Throat.

Strep A infection affects the throat and tonsils. It spreads from person to person through coughing or sneezing.

Strep throat is most common in children 5 to 15 years old, but it can also affect older.4

Strep throat can be treated with antibiotics. Leaving the infection untreated can lead to severe complications such pneumonia, scarlet fever, sepsis, and streptococcal toxic shock.3

A child has a Strep Throat and is holding by his neck because his throat hurts.
Strep Throat.

What is the difference between Strep Throat and Sore Throat?

A Strep Throat is a Sore Throat caused by Group A Streptococcus.

The dominant causes of sore throats are viruses (rhinoviruses, coronaviruses, and others). When it comes to bacterial infection, Strep A is the prevalent cause.5 A sore throat can also result from allergies, various irritants or diseases.

Only around 30 % of children and 10 % of adults with a sore throat have strep throat.5

Sometimes it is hard to distinguish between viral and bacterial throat infections based on the symptoms alone. Therefore, visiting a doctor and performing appropriate examinations, including a Strep A test, is essential.

A collage of people with sore throat.
Strep Throat or Sore Throat?

What are the symptoms of Strep A infection?

Common symptoms of Strep A infection are:

  • Sore Throat that starts quickly with pain when swallowing,
  • fever,
  • red and swollen tonsils, some with white patches or streaks of pus,
  • tiny red spots on the roof of the mouth (the palate),
  • swollen cervical lymph nodes.

Sometimes the infection manifests as a cough, runny nose, hoarseness, and conjunctivitis (pink eye).

Most Strep A infections are mild and easily treated. Approximately 15-20% of children do not develop symptoms.6 But in some cases, Strep A can cause severe complications. Therefore, it is crucial to assess and treat the condition appropriately. 

How infectious is Strep A?

Streptococci A bacteria are very infectious. Infection primarily spreads through direct contact with respiratory secretions.7

Infected people are contagious for about 2-5 days8, and they transmit the bacteria to others within this time. Talking, sneezing, or coughing is enough to spread the infection.

Strep A can also spread through food not appropriately handled or via infected surfaces such as toys or cutlery.

What are the preventive measures against Strep A infection?

Preventive measures against Strep A infection are simple and easy to follow. It is essential to maintain good personal hygiene.

The most important is to wash your hands regularly, especially after coughing or sneezing and before preparing the food.

Cover your mouth when sneezing or coughing to decrease the number of droplets spreading into the surroundings.

Don’t share your items with others. Your respiratory secretions (saliva, nasal discharge) are most probably attached to the surfaces of these items.

How is Strep Throat diagnosed?

Doctors typically diagnose Strep Throat with a physical examination, considering symptoms, and with the Strep A test – a rapid Strep A test or a conventional culture method. The prerequisite of both techniques is a throat swab.

  • Rapid Strep A test. It is a method of choice for doctors; you can also do the test at home. The test detects Streptococcus pyogenes antigens in a throat swab. It is highly accurate, easy to use and economically accessible. The test takes 5 minutes to perform, and then there is a waiting time of 10 minutes for the result.
  • Culture method. This conventional method checks directly for Streptococcus pyogenes bacteria in the sample. The sample is cultured in a laboratory on a culturing medium and observed if some S. pyogenes will grow. This method provides more accurate results than a rapid antigen test, but it can take 18 –  48 hours to get results.9

Why should you want to know if a Strep A infection is causing your Sore Throat?

Knowing the cause of a Sore Throat is vital to decide on the appropriate treatment. Treatment of a bacterial throat infection differentiates from treating a viral throat infection. Antibiotics do not work against viruses.

If viruses are causing Sore Throat, the infection will usually resolve independently. Your doctor will recommend symptomatic treatment to support the recovery process.

If bacteria are causing Sore Throat (most probably Streptococci A), your doctor will consider treatment with antibiotics.

The infection spreads very fast. Early diagnosis and treatment are essential to prevent the spread and potentially severe health complications.

Therefore, for applying the proper treatment, it is essential to know whether the cause of a sore throat is a bacterial or viral infection.

Testing for Strep A at home – pros and cons?

At-home rapid strep throat testing can be beneficial in diagnosing an infection. The test is fast, simple, and relatively inexpensive. However, while it is a valuable tool in diagnosing strep throat, it is not 100 % accurate. It should not be considered a replacement for a more comprehensive medical evaluation.

Pros

  • The main advantage of the Strep A home test is that you can do it yourself at home.
  • The test is quick and easy to perform. It is the same rapid test as doctors use.
  • The results are available within minutes.
  • It is relatively inexpensive.

Cons 

  • Rapid Strep A test is not 100% accurate (the same applies to rapid Strep A home test or the one doctors perform). There is a slight chance that the test will give a false positive or false negative result.
  • It is impossible to control if a person collects the sample properly at home. People should always strictly follow the instructions for use.
  • Rapid Strep A tests cannot detect other causes of sore throats.
  • The insurance may not cover the test, so you must bear the cost. At your physician, you might get it for free.

You should always purchase the test kit from a reputable source. Reliability and testing experience can differ significantly between various brands. 

Overall, testing for Strep throat at home is a great way to decide whether a sore throat is a streptococcal infection. Still, it should not be a substitute for seeing your doctor.

Take-home points

  • The bacteria Streptococcus pyogenes causes strep throat.
  • Strep throat is not the same as Sore Throat.
  • Streptococcus A is the most common cause of angina.
  • Infection is usually transmitted with respiratory droplets.
  • Strep throat is most common in children 5 to 15 years old.
  • About 15-20% of children do not experience any symptoms.
  • Only about 30 % of children and 10 % of adults with a sore throat have strep throat.
  • Infected people are contagious for about 2-5 days.
  • Strep A is cured with antibiotics. Antibiotics do not work against viruses.
  • Viral sore throats usually clear on their own.
  • Strep throat is diagnosed with the help of rapid Strep A test.
  • You can do the Strep A test at home.

References

  1. Patterson MJ. Streptococcus. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 13. Available from: https://www.ncbi.nlm.nih.gov/books/NBK7611/
  2. Kanwal S, Vaitla P. Streptococcus Pyogenes. [Updated 2022 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554528/
  3. Avire NJ, Whiley H, Ross K. A Review of Streptococcus pyogenes: Public Health Risk Factors, Prevention and Control. Pathogens. 2021 Feb 22;10(2):248. doi: 10.3390/pathogens10020248. PMID: 33671684; PMCID: PMC7926438.
  4. National Center for Immunization and Respiratory Diseases, Division of Bacterial Diseases. June 27, 2022.
  5. Ashurst JV, Edgerley-Gibb L. Streptococcal Pharyngitis. [Updated 2022 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK525997/
  6. Othman AM, Assayaghi RM, Al-Shami HZ, Saif-Ali R. Asymptomatic carriage of Streptococcus pyogenes among school children in Sana’a city, Yemen. BMC Res Notes. 2019 Jun 14;12(1):339. doi: 10.1186/s13104-019-4370-5. PMID: 31200755; PMCID: PMC6570875.
  7. Langlois D. M., Andreae M. (2011). Group A streptococcal infections. Pediatr. Rev. 32 (10), 423–9; quiz 30. 10.1542/pir.32-10-423
  8. Snow V., Mottur-Pilson C., Cooper R. J., Hoffman J. R. (2001). Principles of appropriate antibiotic use for acute pharyngitis in adults. Ann. Intern. Med. 134 (6), 506–508.
  9. Thompson TZ, McMullen AR. Group A Streptococcus Testing in Pediatrics: the Move to Point-of-Care Molecular Testing. J Clin Microbiol. 2020 May 26;58(6):e01494-19. doi: 10.1128/JCM.01494-19. PMID: 32161094; PMCID: PMC7269410.
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