Streptococcal pharyngitis

The typical signs and symptoms of streptococcal pharyngitis are a sore throat, fever of greater than 38 °C (100 °F), tonsillar exudates (pus on the tonsils), and large cervical lymph nodes.^[14]

Other symptoms include: headache, nausea and vomiting, abdominal pain,^[15] muscle pain,^[16] or a scarlatiniform rash or palatal petechiae, the latter being an uncommon but highly specific finding.^[14]

Symptoms typically begin one to three days after exposure and last seven to ten days.^[3][14]

Strep throat is unlikely when any of the symptoms of red eyes, hoarseness, runny nose, or mouth ulcers are present. It is also unlikely when there is no fever.^[9]

• 
  Mouth wide open showing the throat
  A throat infection which on culture tested positive for group A streptococcus. Note the large tonsils with white exudate.
• 
  Mouth wide open showing the throat
  Note the petechiae, or small red spots, on the soft palate. This is an uncommon but highly specific finding in streptococcal pharyngitis.^[14]
• 
  A set of large tonsils in the back of the throat, covered in white exudate.
  This is a culture-positive case of streptococcal pharyngitis with typical tonsillar exudate in an 8-year-old.

Strep throat is caused by group A β-hemolytic Streptococcus (GAS or S. pyogenes).^[17] Humans are the primary natural reservoir for group A streptococcus.^[18] Other bacteria such as non–group A β-hemolytic streptococci and fusobacterium may also cause pharyngitis.^[14][16] It is spread by direct, close contact with an infected person; thus crowding, as may be found in the military and schools, increases the rate of transmission.^[16][19] Dried bacteria in dust are not infectious, although moist bacteria on toothbrushes or similar items can persist for up to fifteen days.^[16] Contaminated food can result in outbreaks, but this is rare.^[16] Of children with no signs or symptoms, 12% carry GAS in their pharynx,^[8] and, after treatment, approximately 15% of those remain positive, and are true "carriers".^[20]

A number of scoring systems exist to help with diagnosis; however, their use is controversial due to insufficient accuracy.^[21] The modified Centor criteria are a set of five criteria; the total score indicates the probability of a streptococcal infection.^[14]

One point is given for each of the criteria:^[14]

• 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)

A score of one may indicate no treatment or culture is needed or it may indicate the need to perform further testing if other high risk factors exist, such as a family member having the disease.^[14]

The Infectious Disease Society of America recommends against routine antibiotic treatment and considers antibiotics only appropriate when given after a positive test.^[9] Testing is not needed in children under three as both group A strep and rheumatic fever are rare, unless a child has a sibling with the disease.^[9]

Laboratory testing

A throat culture is the gold standard^[22] for the diagnosis of streptococcal pharyngitis, with a sensitivity of 90–95%.^[14] A rapid strep test (also called rapid antigen detection testing or RADT) may also be used. While the rapid strep test is quicker, it has a lower sensitivity (70%) and statistically equal specificity (98%) as a throat culture.^[14] In areas of the world where rheumatic fever is uncommon, a negative rapid strep test is sufficient to rule out the disease.^[23]

A positive throat culture or RADT in association with symptoms establishes a positive diagnosis in those in which the diagnosis is in doubt.^[24] In adults, a negative RADT is sufficient to rule out the diagnosis. However, in children a throat culture is recommended to confirm the result.^[9] Asymptomatic individuals should not be routinely tested with a throat culture or RADT because a certain percentage of the population persistently "carries" the streptococcal bacteria in their throat without any harmful results.^[24]

Differential diagnosis

As the symptoms of streptococcal pharyngitis overlap with other conditions, it can be difficult to make the diagnosis clinically.^[14] Coughing, nasal discharge, diarrhea, and red, irritated eyes in addition to fever and sore throat are more indicative of a viral sore throat than of strep throat.^[14] The presence of marked lymph node enlargement along with sore throat, fever, and tonsillar enlargement may also occur in infectious mononucleosis.^[25] Other conditions that may present similarly include epiglottitis, Kawasaki disease, acute retroviral syndrome, Lemierre's syndrome, Ludwig's angina, peritonsillar abscess, and retropharyngeal abscess.^[5]

Tonsillectomy may be a reasonable preventive measure in those with frequent throat infections (more than three a year).^[26] However, the benefits are small and episodes typically lessen in time regardless of measures taken.^[27][28][29] Recurrent episodes of pharyngitis which test positive for GAS may also represent a person who is a chronic carrier of GAS who is getting recurrent viral infections.^[9] Treating people who have been exposed but who are without symptoms is not recommended.^[9] Treating people who are carriers of GAS is not recommended as the risk of spread and complications is low.^[9]

Untreated streptococcal pharyngitis usually resolves within a few days.^[14] Treatment with antibiotics shortens the duration of the acute illness by about 16 hours.^[14] The primary reason for treatment with antibiotics is to reduce the risk of complications such as rheumatic fever and retropharyngeal abscesses.^[14] Antibiotics prevent acute rheumatic fever if given within 9 days of the onset of symptoms.^[17]

Pain medication

Pain medication such as NSAIDs and paracetamol (acetaminophen) helps in the management of pain associated with strep throat.^[30] Viscous lidocaine may also be useful.^[31] While steroids may help with the pain,^[17][32] they are not routinely recommended.^[9] Aspirin may be used in adults but is not recommended in children due to the risk of Reye syndrome.^[17]

Antibiotics

The antibiotic of choice in the United States for streptococcal pharyngitis is penicillin V, due to safety, cost, and effectiveness.^[14] Amoxicillin is preferred in Europe.^[33] In India, where the risk of rheumatic fever is higher, intramuscular benzathine penicillin G is the first choice for treatment.^[17]

Appropriate antibiotics decrease the average 3–5 day duration of symptoms by about one day, and also reduce contagiousness.^[24] They are primarily prescribed to reduce rare complications such as rheumatic fever and peritonsillar abscess.^[34] The arguments in favor of antibiotic treatment should be balanced by the consideration of possible side effects,^[16] and it is reasonable to suggest that no antimicrobial treatment be given to healthy adults who have adverse reactions to medication or those at low risk of complications.^[34][35] Antibiotics are prescribed for strep throat at a higher rate than would be expected from how common it is.^[36]

Erythromycin and other macrolides or clindamycin are recommended for people with severe penicillin allergies.^[14][9] First-generation cephalosporins may be used in those with less severe allergies^[14] and some low-certainty evidence suggest cephalosporins are superior to penicillin.^[37][38] These late-generation antibiotics show a similar effect when prescribed for 3–7 days in comparison to the standard ten days of penicillin when used in areas of low rheumatic heart disease.^[39] Streptococcal infections may also lead to acute glomerulonephritis; however, the incidence of this side effect is not reduced by the use of antibiotics.^[17]

The symptoms of strep throat usually improve within three to five days, irrespective of treatment.^[24] Treatment with antibiotics reduces the risk of complications and transmission; children may return to school 24 hours after antibiotics are administered.^[14] The risk of complications in adults is low.^[9] In children, acute rheumatic fever is rare in most of the developed world. It is, however, the leading cause of acquired heart disease in India, sub-Saharan Africa, and some parts of Australia.^[9]

Complications arising from streptococcal throat infections include:

The economic cost of the disease in the United States in children is approximately $350 million annually.^[9]

Pharyngitis, the broader category into which Streptococcal pharyngitis falls, is diagnosed in 11 million people annually in the United States.^[14] It is the cause of 15–40% of sore throats among children^[8][14] and 5–15% in adults.^[9] Cases usually occur in late winter and early spring.^[14]