Strep Throat Latest Facts: Etiology, Symptoms, Diagnosis and Treatment

Strep throat or Streptococcal pharyngitis is the infection and inflammation of the throat, including the tonsils by Group A Streptococcus (GAS) bacteria. It is transmitted through respiratory droplets via coughing and sneezing. Strep has a climate preference for late winter and early spring. It infects with an age preference predominantly affecting children between the ages of 5 and 15. However, it can cause infections in individuals of all ages. It is highly contagious, due to its potential human-to-human transmission. It can also be transmitted by sharing utensils or consumption of contaminated food. Being a very common and contagious infection it affects approximately 11 million people in the US annually.

Strep Throat

Strep Throat. Image Courtesy of James Heilman, MD

An infected person may be contagious even before symptoms begin to appear, and this asymptomatic infectious period lasts for 2-5 days. This period is referred to as the incubation period of the infection, and patients remain undiagnosed during this period. Due to this, the infection rate can increase rapidly in communities as infected individuals are unaware of their condition and may share utensils or be in physical contact with others facilitating the transmission of strep. Strep may also be transmitted by contact with skin wounds infected by GAS bacteria. Prevention of this infectious disease requires proper physical hygiene, not sharing any utensils, and covering of mouth while coughing and sneezing.

Etiology of Strep Throat

Streptococcal pharyngitis is caused by GAS bacteria or Streptococcus pyogenes. Other bacterial etiologies include non-group A, beta-hemolytic Streptococci, and fusobacterium. Crowded spaces allow for easier transmission of this airborne infection, hence the increased rate of transmission in schools and the military.

Although there is no vaccine to prevent this infection, it can be treated with antibiotics. However, even after treatment, around 15% of infected individuals may test positive for GAS bacteria. They are referred to as, ‘carriers’.

Symptoms of Strep Pharyngitis

Strep throat is a bacterial infection presenting with its classical symptoms and also with constitutional symptoms. The typical symptoms of strep pharyngitis are sore throat, sudden onset fever (greater than 38 degrees), red tonsils with white patches (exudative tonsils), and cervical lymphadenopathy.

Patients may also present with headaches, loss of appetite, dysphagia, abdominal pain, muscle pain, nausea and vomiting, and rash.

Symptoms start appearing 3 to 5 days post-exposure and stay for 7 to 10 days. Patients may also develop Scarlet Fever, which is characterized by the presence of high fever, sore throat, and a bright red rash over the body, and the typical ‘strawberry tongue’ of scarlatina.

Diagnosis of Strep Throat

Strep pharyngitis has specific symptoms that increase suspicion for diagnosis in affected patients. The first step for diagnosis is the physical examination, allowing the physician to view the throat and the characteristic exudative lesions on the tonsils.

Physicians may also use the Modified Centor Criteria which indicates the probability of a sore throat being strep pharyngitis. The modified Centor Criteria is a set of 5 specific criteria:

  • Absence of a cough
  • Swollen and tender cervical lymph nodes
  • Temperature >38.0 °C (100.4 °F)
  • Tonsillar exudate or swelling
  • Age less than 15 (a point is subtracted if age >44)

The presence of each criterion adds a point to the overall score, a score of less than or equal to one has a low probability of being strep pharyngitis, and no treatment or bacterial culture for further diagnosis is needed. A score of 5 indicates the need for empirical antibiotic treatment.

The gold standard for diagnosis of Strep is throat culture, with a sensitivity of 90-95%. A rapid antigen detection test (rapid strep test) can also be done for the diagnosis, it is usually quicker, however, has a sensitivity of only 70%.

In an adult, diagnosis of strep pharyngitis can be excluded if the rapid strep test is negative whereas, for a child, diagnosis can only be excluded if culture is negative.

Differential Diagnosis

The symptoms of Strep pharyngitis are very common and overlap with the symptoms of other disorders, making a clinical diagnosis alone difficult. Some of the conditions that present similar to strep are mentioned below:

  • Viral Sore throat (present with coughing, diarrhea, and watery eyes, along with strep-like symptoms)
  • Infectious Mononucleosis (characteristic cervical lymphadenopathy seen)
  • Epiglottitis
  • Kawasaki Disease
  • Acute Retroviral Syndrome
  • Peritonsillar abscess
  • Retropharyngeal abscess

Treatment of Strep Throat

Strep pharyngitis is a self-limiting disease and usually resolves in a few days if left untreated. The use of antibiotics doesn’t necessarily reduce the duration of disease but it is recommended regardless, with the aim of reducing post-infectious complications.

The drug of choice for the treatment of strep pharyngitis is Penicillin V. It is used for its efficiency, safety, and low cost. If treatment is started within 9 days of infection, the risk of developing rheumatic fever decreases significantly.

In case of allergies to Penicillin V, patients may be given cephalosporins instead. Some studies show cephalosporins to be more efficient than penicillin, however, no conclusive results have been published yet.

In case of severe allergies to Penicillin, Erythromycin or Clindamycin may be given instead.

It is important to note that if an adult patient has a low risk for complications, and is allergic to the recommended antibiotics, no antibiotic treatment is given. In fact, the FDA strictly recommends the appropriate use of antibiotics, especially now in the era of antibiotic resistance. They recommend against empiric antibiotics use unless a rapid strep test has come positive. Treating with antibiotics based on suspicion of strep is no longer allowed.

Patients may also be given NSAIDs like acetaminophen to help with pain management. Aspirin may also be used, but only in adults and not children for the fear of Reye’s Syndrome.

Complications of Strep Throat

If left untreated, strep pharyngitis can lead to several complications, however, these are rare in adults. It can lead to the development of:

  1. Ear infections and recurrent infections
  2. Sinusitis
  3. Mastoiditis
  4. Acute Rheumatic Fever
  5. Post Streptococcal Glomerulonephritis

My opinion

It is a very common infection caused by Group A Streptococcus. It is also a self-limited disease and does not warrant the need for antibiotics, especially in mild cases. It is common knowledge that the unnecessary use of antibiotics can lead to antibiotic-resistant bacteria.

Also, it is important for patients to get a follow-up checkup to ensure that strep infection hasn’t caused a major, non-infectious complication like rheumatic fever or post-streptococcal glomerulonephritis. It is important to look for and treat these diseases if present as they can cause dire consequences.  


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