Pharyngitis

Background

Anatomy of the posterior pharynx.

• 1-2% of all ED visits
• Viral is most common cause (~70% in children, ~90% in adults)
  • Exudates do not mean bacterial — most common cause of exudative pharyngitis is still viral
  • Common viral etiologies: Rhinovirus, Coronavirus, Adenovirus, Influenza, Coxsackievirus, EBV
• Bacterial causes:
  • Group A Streptococcus (GAS): most important bacterial cause
  • Group C and G Streptococcus: can cause pharyngitis but do not cause acute rheumatic fever
  • Fusobacterium necrophorum: increasingly recognized cause in adolescents/young adults (may cause up to 10-20% of pharyngitis in this age group); can lead to Lemierre's syndrome
  • Neisseria gonorrhoeae: consider in sexually active patients with pharyngitis and relevant exposure history
  • Corynebacterium diphtheriae: rare in developed countries; consider in unvaccinated or recent travelers

Streptococcal pharyngitis

• Accounts for 5-15% of pharyngitis in adults and 15-30% in children
• Peak incidence in ages 5-15 years
• Rare in children <3 years of age (typically presents as "streptococcosis" with rhinitis/low-grade fever rather than classic pharyngitis)
• Seasonal: winter and early spring
• Treatment can be delayed for up to 9 days from symptom onset and still prevent acute rheumatic fever

Clinical Features

Generalized erythema of the pharynx, consistent with pharyngitis.

Culture positive strep pharyngitis with typical tonsillar exudate

General

• Sore throat
• Painful swallowing (odynophagia)
• Fever
• Nausea and vomiting
• Tonsillar exudate
• Anterior cervical lymphadenopathy
• Palatal petechiae

Features Favoring Bacterial (GAS) Etiology

• Sudden onset sore throat
• Fever ≥38.3°C (101°F)
• Tonsillar exudate
• Tender anterior cervical lymphadenopathy
• Absence of cough, rhinorrhea, conjunctivitis, hoarseness, or oral ulcers

Features Favoring Viral Etiology

• Cough
• Rhinorrhea
• hoarseness
• Oral ulcers
• Conjunctivitis
• Diarrhea
• Characteristic viral exanthems (e.g., hand-foot-and-mouth disease)
• Viral symptoms reduce likelihood but do not exclude GAS (test positivity still ~23-28% with viral symptoms present)

Classic Clues for Specific Diagnoses

• Post-treatment with amoxicillin/ampicillin → diffuse pruritic maculopapular rash = classic for EBV pharyngitis (infectious mononucleosis)
• Unilateral sore throat, "hot potato" voice, trismus, uvular deviation = peritonsillar abscess
• Sore throat with high fever progressing to unilateral neck swelling/pain and sepsis in a young adult = consider Lemierre's syndrome
• Gray pharyngeal membrane in unvaccinated patient = Diphtheria
• Vesicular/ulcerative lesions on posterior pharynx = Herpangina or HSV
• Pharyngitis with splenomegaly, posterior cervical lymphadenopathy, fatigue = infectious mononucleosis
• Pharyngitis with diffuse lymphadenopathy, rash, oral ulcers = consider acute HIV

Modified Centor Criteria

One point is given for each of the criteria:

1. Absence of a cough
2. Swollen and tender cervical lymph nodes
3. Temperature >38.0 °C (100.4 °F)
4. Tonsillar exudate or swelling
5. Age less than 15^
   • Subtract a point if age >44

Modified Centor score

Points	Probability of Streptococcal pharyngitis
1 or fewer	<10%
2	11–17%
3	28–35%
4 or 5	52%

ED Red Flags

• Stridor, drooling, tripoding → evaluate for epiglottitis, retropharyngeal abscess, or other airway emergency
• Inability to tolerate secretions or worsening dysphagia
• Toxic appearance / signs of sepsis
• Unilateral neck swelling with persistent high fevers → consider Lemierre's syndrome or deep neck space infection
• Floor of mouth swelling → Ludwig's angina
• Trismus → peritonsillar abscess, deep neck space infection

Complications

Suppurative

• Peritonsillar abscess
• Retropharyngeal abscess
• Cervical lymphadenitis
• Mastoiditis
• Lemierre's syndrome (septic thrombophlebitis of the internal jugular vein)

Nonsuppurative

• Acute rheumatic fever (prevented by antibiotics if started within 9 days)
• Post-streptococcal glomerulonephritis (NOT prevented by antibiotics)
• Scarlet fever
• Toxic shock syndrome
• Pediatric autoimmune neuropsychiatric disorder associated with group A streptococci (PANDAS)

Differential Diagnosis

Acute Sore Throat

Bacterial infections

• Streptococcal pharyngitis (Strep Throat)
• Neisseria gonorrhoeae
• Diphtheria (C. diptheriae)
• Bacterial Tracheitis

Viral infections

• Infectious mononucleosis (EBV)
  • Patients with peritonsillar abscess have a 20% incidence of mononucleosis
• Laryngitis
• Acute Bronchitis
• Rhinovirus
• Coronavirus
• Adenovirus
• Herpesvirus
• Influenza virus
• Coxsackie virus
  • Herpangina
  • Hand-foot-and-mouth disease
• HIV (Acute Retroviral Syndrome)

Noninfectious

• Stevens-Johnson Syndrome
• Pemphigus
• Angioedema

Other

• Deep neck space infection
  • Retropharyngeal abscess
  • Ludwig's angina
  • Parapharyngeal space infection
• Peritonsillar Abscess (PTA)
• Epiglottitis
• Kawasaki disease
• Penetrating injury
• Caustic ingestion
• Lemierre's syndrome
• Peritonsillar cellulitis
• Lymphoma
• Internal carotid artery aneurysm
• Oral Thrush
• Parotitis
• Post-tonsillectomy hemorrhage
• Vincent's angina
• Acute necrotizing ulcerative gingivitis

Oral rashes and lesions

• Angioedema
• Aphthous stomatitis
• Herpes gingivostomatitis
• Herpes labialis
• Measles (Koplik's spots)
• Perioral dermatitis
• Oral thrush
• Steven Johnson syndrome
• Streptococcal pharyngitis
• Tongue diagnoses
• Vincent's angina

Evaluation

Rapid Antigen Detection Test Algorithm for Acute Pharyngitis

Category	Testing and Treatment
Clinical features strongly suggesting viral etiology (eg. cough, rhinorrhea, hoarseness, oral ulcers)	None
<3 years old	None because immature immune system not mature enough to develop anti-streptolysin O (ASO) antibodies and acute rheumatic fever. Unless they have a special risk factor (e.g. older sibling with GAS infection)
CENTOR = 1	None
None of the above with CENTOR ≥2	Send rapid antigen detection test Positive = treat Negative Children and adolescents Send back up throat culture (treat later, if positive) Adults None (no need for back up throat culture)

Diagnostic testing or empiric treatment of asymptomatic household contacts of patients with acute streptococcal pharyngitis is not routinely recommended

Key Evaluation Principles

• Do not test patients with clear viral features (cough, rhinorrhea, hoarseness, oral ulcers, conjunctivitis) — treat supportively
• Do not routinely test children <3 years of age (both GAS and acute rheumatic fever are rare), unless risk factors (e.g., sibling with GAS)
• The 2025 IDSA guideline update recommends using a standardized clinical scoring system (e.g., Modified Centor/McIsaac) to identify low-risk patients who do not need testing
• For those meeting testing criteria: use Rapid Antigen Detection Test (RADT)
  • RADT sensitivity 70-90%, specificity >95%
  • In children/adolescents: a negative RADT should be backed up with a throat culture (higher false-negative rate)
  • In adults: backup throat culture generally not required (lower incidence and lower risk of acute rheumatic fever)
• Centor/McIsaac score of 0-1: do not test, treat symptomatically
• Centor/McIsaac score of ≥2: test with RADT (± backup culture in children)
• Do not test asymptomatic contacts routinely
• Do not perform test of cure after treatment unless history of acute rheumatic fever or recurrent GAS complications

Additional Testing to Consider (When Clinically Indicated)

• Monospot / heterophile antibody for suspected infectious mononucleosis (note: 25% false-negative in first 10 days of illness)
• Gonorrhea NAAT for suspected gonococcal pharyngitis
• CT neck with contrast if concern for deep neck space infection, peritonsillar abscess, or Lemierre's syndrome
• HIV testing if risk factors and clinical features suggest acute retroviral syndrome

Management

Symptomatic Treatment

• Analgesics/antipyretics are the foundation of treatment for ALL pharyngitis (viral and bacterial)
  • Ibuprofen 400-600mg PO q6h PRN (adults); 10 mg/kg PO q6h PRN (pediatric)
  • Acetaminophen 1000mg PO q6h PRN (adults); 15 mg/kg PO q4-6h PRN (pediatric)
  • Ibuprofen may be slightly more effective for throat pain than acetaminophen
  • Avoid aspirin in children (Reye syndrome)
• Topical therapies:
  • Salt water gargle
  • Viscous lidocaine (adults) — use with caution due to aspiration risk
  • Consider "magic mouthwash" (diphenhydramine/lidocaine/antacid mixture)
• Hydration: encourage oral fluids, soft diet; assess ability to tolerate PO before discharge

Antibiotics

Treatment can be delayed for up to 9 days and still prevent major sequelae

Penicillin Options:

• Penicillin V 250mg PO BID x 10d (child) or 500mg BID x 10d (adolescent or adult)
• Bicillin L-A <27 kg: 0.6 million units; ≥27 kg: 1.2 million units IM x 1
• Amoxicillin 50 mg/kg once daily (maximum = 1000 mg) for 10 days

Penicillin allergic (mild):

• Cephalexin 20 mg per kg PO BID (maximum 500 mg per dose) x 10 days
• Cefadroxil 30 mg per kg PO QD (maximum 1 g daily) x 10 days

Penicillin allergic (anaphylaxis):

• Clindamycin 7 mg/kg/dose TID (maximum = 300 mg/dose) x 10 days
• Azithromycin 12 mg/kg PO once (maximum = 500 mg), then 6 mg/kg (max=250 mg) once daily for the next 4 days
• Clarithromycin 7.5 mg/kg/dose PO BID (maximum = 250 mg/dose) x 10 days

Pediatric Dosing:

• Amoxicillin 50mg/kg PO once daily x 10 days (max 1000mg)
• Penicillin V <27kg: 250mg PO BID-TID x 10 days; >27kg: 500mg PO BID-TID x 10 days
• Penicillin G Benzathine <27kg: 600,000 units IM x 1; >27kg: 1.2 million units IM x 1
• PCN allergy (mild): Cephalexin 20mg/kg PO BID x 10 days (max 500mg/dose)
• PCN allergy (mild): Cefadroxil 30mg/kg PO daily x 10 days (max 1g)
• PCN allergy (severe): Azithromycin 12mg/kg PO day 1 (max 500mg), then 6mg/kg daily x 4 days (max 250mg)
• PCN allergy (severe): Clindamycin 7mg/kg/dose PO TID x 10 days (max 300mg/dose)
• PCN allergy (severe): Clarithromycin 7.5mg/kg PO BID x 10 days (max 250mg/dose)

• Clindamycin 7mg/kg/dose PO q8h x 10 days; Max: 300mg/dose
• Azithromycin Children ≥2 years and Adolescents: Oral: 12mg/kg/dose once daily for 5 days (maximum: 500mg daily)
• Amoxicillin 50mg/kg PO q24h x 10 days; Max: 1000mg/day
• Clarithromycin >6mo: 15mg/kg/day PO divided q12h x 7-10d
• Cephalexin 40mg/kg/day PO divided q12h x 10 days; Max: 500mg/dose
• Cefpodoxime 100mg q 12 h for 5-10 days
• Cefuroxime 250mg PO bid x10 days
• Cefuroxime 250mg PO bid x10 days

• Treatment is indicated for laboratory-confirmed GAS pharyngitis (RADT or culture positive)
• Do not treat empirically based on clinical features alone in most cases
• Goal: prevent acute rheumatic fever, reduce suppurative complications, improve symptoms, decrease transmission
• Key point: antibiotics shorten symptom duration by approximately 1-2 days when started early

Steroids

• In adults consider single dose of dexamethasone 0.6mg/kg PO (Max = 10mg)
  • Reduces pain severity and time to onset of pain relief (~4-12 hours faster resolution)
• In children consider single dose of dexamethasone 0.6mg/kg PO (Max = 10mg)
• Note: The 2012 IDSA guideline did not recommend routine adjunctive corticosteroids; however, emergency medicine literature supports their use for pain relief

Disposition

Discharge (Majority of Patients)

• Discharge home with symptomatic treatment ± antibiotics
• Patient can return to work/school after ≥24 hours of antibiotic therapy and clinical improvement (for confirmed GAS)
• Return precautions:
  • Unable to tolerate oral fluids
  • Worsening sore throat or new difficulty swallowing despite treatment
  • Difficulty breathing or changes in voice
  • Persistent or worsening fever after 48 hours of antibiotics
  • New unilateral neck swelling or stiffness

Consider Admission

• Inability to tolerate oral fluids (especially in children) → IV hydration
• Concern for airway compromise
• Sepsis or toxic appearance
• Suspected deep neck space infection, Lemierre's syndrome, or other suppurative complication requiring IV antibiotics and imaging

ED Pearls

• Most sore throats are viral — focus on symptom management and avoid unnecessary antibiotics
• Centor Criteria help identify who does NOT need testing (score 0-1), not who has strep
• Exudate ≠ bacterial; viral pharyngitis frequently causes exudates
• Treatment for GAS can be safely delayed up to 9 days and still prevent acute rheumatic fever — you do not need to prescribe empiric antibiotics from the ED without testing
• Think about Fusobacterium necrophorum and Lemierre's syndrome in any adolescent or young adult with a prolonged, severe, or worsening sore throat, especially with lateral neck pain/swelling or signs of sepsis
• Post-streptococcal glomerulonephritis is NOT prevented by antibiotic treatment (unlike acute rheumatic fever)
• Infectious mononucleosis + amoxicillin/ampicillin = maculopapular rash (present in up to 70-100% of cases)
• Consider acute HIV in any patient with a mononucleosis-like illness and negative Monospot
• Always assess for ability to tolerate PO fluids before discharging pharyngitis patients, particularly young children

See Also

• Sore Throat
• Streptococcal pharyngitis
• Peritonsillar abscess
• Lemierre's syndrome
• Infectious mononucleosis
• Retropharyngeal abscess
• Epiglottitis
• EBQ:TOAST Trial

References

📊 Centor/McIsaac Score Calculator [show]

Centor/McIsaac Score

Modified Centor (McIsaac) Score

Criteria	No (0)	Yes (+1)
Tonsillar exudates or swelling	0	1
Tender/swollen anterior cervical lymph nodes	0	1
Temperature >38°C (100.4°F)	0	1
Absence of cough	0	1
Age modifier (McIsaac modification)
Age 3–14 years	0	1 (+1)
Age 15–44 years	(0 points — default)
Age ≥45 years	0	-1 (−1)
Modified Centor Score	0   / 5

Interpretation & Management
≤0	~1–2.5% strep probability — No testing or antibiotics needed.
1	~5–10% strep probability — No testing or antibiotics needed (optional rapid strep if high clinical suspicion).
2–3	~11–35% strep probability — Rapid strep testing recommended; treat if positive.
4–5	~51–53% strep probability — Consider empiric antibiotics or rapid strep test.

References
Centor RM et al. The diagnosis of strep throat in adults. Med Decis Making. 1981;1:239-246. PMID 6763125. McIsaac WJ et al. A clinical score to reduce unnecessary antibiotic use. CMAJ. 1998;158:75-83. PMID 9475915.