Streptococcal pharyngitis

Streptococcal pharyngitis, also known as strep throat, or Bacterial tonsillitis is an infection of the back of the throat including the tonsils caused by group A streptococcus (GAS).[1] Common symptoms include fever, sore throat, red tonsils (tonsilitis), and enlarged lymph nodes in the neck.[1] A headache, and nausea or vomiting may also occur.[1] Some develop a sandpaper-like rash which is known as scarlet fever.[2] Symptoms typically begin one to three days after exposure and last seven to ten days.[2][3]

Streptococcal pharyngitis
Other namesStreptococcal tonsillitis, streptococcal sore throat, strep
A set of large tonsils in the back of the throat covered in white exudate
A culture positive case of streptococcal pharyngitis with typical tonsillar exudate in a 16-year-old.
SpecialtyInfectious disease
SymptomsFever, sore throat, large lymph nodes[1]
Usual onset1–3 days after exposure[2][3]
Duration7–10 days[2][3]
CausesGroup A streptococcus[1]
Risk factorsSharing drinks or eating utensils[4]
Diagnostic methodThroat culture, strep test[1]
Differential diagnosisEpiglottitis, infectious mononucleosis, Ludwig's angina, peritonsillar abscess, retropharyngeal abscess, viral pharyngitis[5]
PreventionHandwashing,[1] covering coughs[4]
TreatmentParacetamol (acetaminophen), NSAIDs, antibiotics[1][6]
Frequency5 to 40% of sore throats[7][8]

Strep throat is spread by respiratory droplets from an infected person.[1] It may be spread directly or by touching something that has droplets on it and then touching the mouth, nose, or eyes.[1] Some people may carry the bacteria without symptoms.[1] It may also be spread by skin infected with group A strep.[1] The diagnosis is made based on the results of a rapid antigen detection test or throat culture in those who have symptoms.[9]

Prevention is by washing hands and not sharing eating utensils.[1] There is no vaccine for the disease.[1] Treatment with antibiotics is only recommended in those with a confirmed diagnosis.[9] Those infected should stay away from other people until fever is gone and for at least 12 hours after starting treatment.[1] Pain can be treated with paracetamol (acetaminophen) and nonsteroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen.[6]

Strep throat is a common bacterial infection in children.[2] It is the cause of 15–40% of sore throats among children[7][10] and 5–15% among adults.[8] Cases are more common in late winter and early spring.[10] Potential complications include rheumatic fever and peritonsillar abscess.[1][2]

Signs and symptoms

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.[10]

Other symptoms include: headache, nausea and vomiting, abdominal pain,[11] muscle pain,[12] or a scarlatiniform rash or palatal petechiae, the latter being an uncommon but highly specific finding.[10]

Symptoms typically begin one to three days after exposure and last seven to ten days.[3][10]

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.[8]


Strep throat is caused by group A β-hemolytic Streptococcus (GAS or S. pyogenes).[13] Humans are the primary natural reservoir for group A streptococcus.[14] Other bacteria such as non–group A β-hemolytic streptococci and fusobacterium may also cause pharyngitis.[10][12] 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.[12][15] Dried bacteria in dust are not infectious, although moist bacteria on toothbrushes or similar items can persist for up to fifteen days.[12] Contaminated food can result in outbreaks, but this is rare.[12] Of children with no signs or symptoms, 12% carry GAS in their pharynx,[7] and, after treatment, approximately 15% of those remain positive, and are true "carriers".[16]


Modified Centor score
Points Probability of Strep Management
1 or fewer <10% No antibiotic or culture needed
2 11–17% Antibiotic based on culture or RADT
3 28–35%
4 or 5 52% Empiric antibiotics

A number of scoring systems exist to help with diagnosis; however, their use is controversial due to insufficient accuracy.[17] The modified Centor criteria are a set of five criteria; the total score indicates the probability of a streptococcal infection.[10]

One point is given for each of the criteria:[10]

  • 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.[10]

The Infectious Disease Society of America recommends against routine antibiotic treatment and considers antibiotics only appropriate when given after a positive test.[8] 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.[8]

Laboratory testing

A throat culture is the gold standard[18] for the diagnosis of streptococcal pharyngitis, with a sensitivity of 90–95%.[10] 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.[10] In areas of the world where rheumatic fever is uncommon, a negative rapid strep test is sufficient to rule out the disease.[19]

A positive throat culture or RADT in association with symptoms establishes a positive diagnosis in those in which the diagnosis is in doubt.[20] In adults, a negative RADT is sufficient to rule out the diagnosis. However, in children a throat culture is recommended to confirm the result.[8] 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.[20]

Differential diagnosis

As the symptoms of streptococcal pharyngitis overlap with other conditions, it can be difficult to make the diagnosis clinically.[10] 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.[10] The presence of marked lymph node enlargement along with sore throat, fever, and tonsillar enlargement may also occur in infectious mononucleosis.[21] 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).[22] However, the benefits are small and episodes typically lessen in time regardless of measures taken.[23][24][25] 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.[8] Treating people who have been exposed but who are without symptoms is not recommended.[8] Treating people who are carriers of GAS is not recommended as the risk of spread and complications is low.[8]


Untreated streptococcal pharyngitis usually resolves within a few days.[10] Treatment with antibiotics shortens the duration of the acute illness by about 16 hours.[10] The primary reason for treatment with antibiotics is to reduce the risk of complications such as rheumatic fever and retropharyngeal abscesses.[10] Antibiotics prevent acute rheumatic fever if given within 9 days of the onset of symptoms.[13]

Pain medication

Pain medication such as NSAIDs and paracetamol (acetaminophen) helps in the management of pain associated with strep throat.[26] Viscous lidocaine may also be useful.[27] While steroids may help with the pain,[13][28] they are not routinely recommended.[8] Aspirin may be used in adults but is not recommended in children due to the risk of Reye syndrome.[13]


The antibiotic of choice in the United States for streptococcal pharyngitis is penicillin V, due to safety, cost, and effectiveness.[10] Amoxicillin is preferred in Europe.[29] In India, where the risk of rheumatic fever is higher, intramuscular benzathine penicillin G is the first choice for treatment.[13]

Appropriate antibiotics decrease the average 3–5 day duration of symptoms by about one day, and also reduce contagiousness.[20] They are primarily prescribed to reduce rare complications such as rheumatic fever and peritonsillar abscess.[30] The arguments in favor of antibiotic treatment should be balanced by the consideration of possible side effects,[12] 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.[30][31] Antibiotics are prescribed for strep throat at a higher rate than would be expected from how common it is.[32]

Erythromycin and other macrolides or clindamycin are recommended for people with severe penicillin allergies.[10][8] First-generation cephalosporins may be used in those with less severe allergies[10] and some low certainty evidence suggest cephalosporins are superior to penicillin.[33][34] These late-generation antibiotics show a similar effect when prescribed for 3–7 days in comparison to the standard 10-days of penicillin when used in areas of low rheumatic heart disease.[35] Streptococcal infections may also lead to acute glomerulonephritis; however, the incidence of this side effect is not reduced by the use of antibiotics.[13]


The symptoms of strep throat usually improve within three to five days, irrespective of treatment.[20] Treatment with antibiotics reduces the risk of complications and transmission; children may return to school 24 hours after antibiotics are administered.[10] The risk of complications in adults is low.[8] 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.[8]


Complications arising from streptococcal throat infections include:

The economic cost of the disease in the United States in children is approximately $350 million annually.[8]


Pharyngitis, the broader category into which Streptococcal pharyngitis falls, is diagnosed in 11 million people annually in the United States.[10] It is the cause of 15–40% of sore throats among children[7][10] and 5–15% in adults.[8] Cases usually occur in late winter and early spring.[10]


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