Key Takeaways
- Approximately 11,000 cases of invasive Group A Streptococcus (GAS) infections, including strep throat precursors, are reported annually in the United States
- Globally, Group A Streptococcus causes over 500,000 deaths yearly, with strep throat as a common non-invasive manifestation affecting millions
- In children aged 5-15 years, strep throat accounts for 15-30% of acute pharyngitis cases in developed countries
- Sudden onset sore throat with fever over 38°C is classic, present in 80-90% of confirmed strep throat cases
- Exudative pharyngitis (white patches) occurs in 50-70% of pediatric strep throat patients
- Tender anterior cervical lymphadenopathy is reported in 60-90% of strep throat cases
- Rapid antigen detection test (RADT) sensitivity is 70-90% for strep throat, higher with throat culture backup
- Throat culture gold standard detects 90-95% GAS in symptomatic patients
- Centor criteria score ≥3 predicts 32-51% strep probability in adults
- Penicillin V 250mg BID x10 days eradicates GAS in 89% of strep throat cases
- Amoxicillin 50mg/kg/day divided TID x10 days cures 92-96% pediatric strep
- Cephalexin 25-50mg/kg/day BID x10 days effective in 90% penicillin-allergic patients
- Rheumatic fever post-strep in 0.3-3% untreated, prevented by antibiotics 70%
- Acute rheumatic fever incidence 25/100,000 in high-risk US populations untreated
- Peritonsillar abscess complicates 0.1-0.2% strep throats, requiring drainage
Strep throat commonly infects children, causing millions of annual cases and serious global health impacts.
Complications and Prevention
- Rheumatic fever post-strep in 0.3-3% untreated, prevented by antibiotics 70%
- Acute rheumatic fever incidence 25/100,000 in high-risk US populations untreated
- Peritonsillar abscess complicates 0.1-0.2% strep throats, requiring drainage
- Post-streptococcal glomerulonephritis (PSGN) follows 1-2% pharyngitis in epidemics
- Pediatric autoimmune neuropsychiatric disorders (PANDAS) linked to 10-20% GABHS infections
- Retropharyngeal abscess rare 0.01%, but mortality 5% if untreated
- Scarlet fever complicates 5-10% strep throats, self-limited rash
- Toxic shock syndrome from GAS post-pharyngitis in <0.1%, mortality 30-70%
- Recurrent strep throat in 20-30% within year if index case not eradicated
- Antibiotic prophylaxis prevents rheumatic fever recurrences by 75% with benzathine penicillin monthly
- Suppurative complications like otitis media in 2-10% untreated children
- Guillain-Barré syndrome post-strep rare, 1-2 per million infections
- Carrier state persists 10-20% post-treatment, non-infectious usually
- Invasive GAS disease risk 3-5x higher post-pharyngitis in adults
- Hand hygiene reduces school transmission by 20-50%
- Necrotizing fasciitis from GAS post-throat 0.001%, amputation 50%
- Secondary prevention penicillin q3-4 weeks reduces ARF attacks 90%
- Vaccine trials show 50-80% efficacy against strep throat, not yet available
- Isolation until 24 hours antibiotics reduces spread 70%
- PSGN seroprevalence 5-10% post-epidemic pharyngitis
- Household transmission 20-50% without prophylaxis
- Rapid testing and treatment cuts complications 40%
- School exclusion 24-48 hours post-antibiotics prevents 30% cases
- ARF latency 2-4 weeks post-strep in 70%
- Carrier treatment with clindamycin prevents recurrent symptoms 80%
- Good sleep hygiene aids recovery, reduces prolonged symptoms 25%
- Prophylaxis for siblings cuts family recurrences 50%
- Global vaccine could prevent 500,000 deaths yearly from GAS sequelae
Complications and Prevention Interpretation
Diagnosis and Testing
- Rapid antigen detection test (RADT) sensitivity is 70-90% for strep throat, higher with throat culture backup
- Throat culture gold standard detects 90-95% GAS in symptomatic patients
- Centor criteria score ≥3 predicts 32-51% strep probability in adults
- Modified Centor score for children: fever, no cough, tender nodes, tonsil swelling scores 1-4 points
- PCR testing for GAS has 95-100% sensitivity and specificity, faster than culture
- McIsaac score incorporates age: +1 for 3-14 years, predicts 10-56% positivity
- False-negative RADT rate 5-30%, necessitating culture in children per IDSA guidelines
- ASO titers rise in 80-85% of untreated strep throat within 3-6 weeks
- Anti-DNase B test more specific for skin infections but 70% sensitive for pharyngitis
- Gram stain of exudate shows gram-positive cocci in chains in 60-80% cases
- Centor score 0: <2.5% strep likelihood; score 4: 56% likelihood
- NAAT (nucleic acid amplification) detects GAS in 2-4 hours with 98% accuracy
- Throat swab must include tonsils/posterior pharynx for 95% culture yield
- Empirical testing recommended for scores ≥2 in low-prevalence settings
- Serology (ASO/DNase) useful for retrospective diagnosis in complications, sensitivity 90%
- Point-of-care RADT reduces antibiotic use by 30% when negative
- Culture incubation 24-48 hours yields beta-hemolytic colonies bacitracin-sensitive in 95%
- Modified Centor for pediatrics: score 3 has 51% PPV, score 1 has 10%
- MALDI-TOF MS identifies GAS in 99% from culture isolates rapidly
- ASO titer >333 IU/mL diagnostic in 80% post-pharyngitis
- Negative predictive value of RADT 95% in low prevalence (<20%)
- Latex agglutination confirms group A antigen in 5 minutes, 90% sensitive
- Clinical prediction rules reduce unnecessary testing by 40%
- Pyrosequencing distinguishes GAS from other beta-hemolytic streps accurately
- In-house RADT kits have 82% sensitivity vs lab 92%
- FeverPAIN score: fever, purulence, attend early, no cough/adenoviral, score 4-5: 60% strep
- Optical immunoassay for GAS 94% specific, 90% sensitive
Diagnosis and Testing Interpretation
Prevalence and Epidemiology
- Approximately 11,000 cases of invasive Group A Streptococcus (GAS) infections, including strep throat precursors, are reported annually in the United States
- Globally, Group A Streptococcus causes over 500,000 deaths yearly, with strep throat as a common non-invasive manifestation affecting millions
- In children aged 5-15 years, strep throat accounts for 15-30% of acute pharyngitis cases in developed countries
- During winter and early spring, strep throat incidence peaks, representing up to 20% of pediatric sore throats in temperate climates
- In the US, about 2.5 million strep throat cases occur yearly, predominantly in school-aged children
- GAS pharyngitis prevalence is 5-10% in adults with sore throat versus 20-30% in children under 15
- In low-income countries, strep throat contributes to 10-15% of acute respiratory infections in children under 5
- School outbreaks of strep throat can affect 20-50% of exposed children within 2-7 days
- In the UK, GP consultations for strep throat total around 1 million annually, peaking at 30 per 1000 children
- Among US military recruits, strep throat incidence reaches 10-20% during basic training seasons
- In Australia, notification rates for GAS pharyngitis are 50-100 per 100,000 population yearly
- Strep throat seasonality shows a 3-fold increase in cases from summer to winter in northern hemispheres
- In Native American communities, strep throat prevalence can exceed 40% during outbreaks
- Europe-wide, strep throat affects 1-5% of the population annually, higher in children
- In China, pediatric strep throat positivity rate is 12-25% among pharyngitis cases
- US hospitalization for strep throat complications occurs in 1-2% of cases, implying 25,000-50,000 admissions yearly
- In South Africa, strep throat seroprevalence in schoolchildren is 15-20%
- Scandinavian countries report 200-300 GAS pharyngitis cases per 100,000 children yearly
- In India, community surveys show 10-15% strep throat carriage in asymptomatic children
- Brazil reports 5-10% of sore throats as strep in urban clinics
- Japan sees 20-30% positivity in winter pediatric pharyngitis
- Canada tracks 1.5-2 million strep throat episodes yearly
- In Israel, daycare strep outbreaks infect 30-60% of attendees
- Russia reports high GAS pharyngitis in 5-10 year olds at 25%
- Mexico urban areas show 8-12% strep throat in primary care sore throats
- New Zealand Maori children have 2-3 times higher strep throat rates than others
- Egypt school surveys find 18% GAS positivity in sore throat cases
- France notifies 300,000-500,000 strep pharyngitis cases yearly
- Germany pediatric incidence is 100-200 per 1000 child-years
- Sore throat, often strep, prompts 15 million US pediatric visits yearly
Prevalence and Epidemiology Interpretation
Symptoms and Clinical Presentation
- Sudden onset sore throat with fever over 38°C is classic, present in 80-90% of confirmed strep throat cases
- Exudative pharyngitis (white patches) occurs in 50-70% of pediatric strep throat patients
- Tender anterior cervical lymphadenopathy is reported in 60-90% of strep throat cases
- Absence of cough distinguishes strep throat likelihood, present in only 10-20% vs 50% in viral
- Scarlet fever rash accompanies 10% of strep throat infections, starting on chest and spreading
- Headache affects 50-70% of children with culture-positive strep pharyngitis
- Abdominal pain occurs in 20-30% of pediatric strep cases, often with nausea
- Petechiae on soft palate seen in 25-50% of strep throat presentations
- Fever duration averages 3-5 days untreated, peaking at 39-40°C in 70% cases
- Dysphagia is severe in 80% of adults with strep pharyngitis
- Halitosis due to tonsillar exudates noted in 40-60% of cases
- Voice changes (muffled) from uvular edema in 30-40% pediatric cases
- Myalgias and arthralgias precede sore throat by 1-2 days in 20% cases
- Rhinorrhea absent in 90% of strep vs present in most viral pharyngitis
- Conjunctivitis rare (<5%) in strep throat, unlike adenovirus
- Fatigue persists 7-10 days post-onset in 50% untreated children
- Strawberry tongue evolves in 20-40% of scarlet fever-associated strep
- Neck stiffness from lymphadenopathy in 70% cases, mimicking meningitis rarely
- Otalgia (referred ear pain) in 10-20% due to shared innervation
- Pallor of palate with circumoral flush in 30% scarlet strep cases
- Anorexia from painful swallowing affects 90% of acute cases
- Hoarseness less common (10%) than in viral laryngitis (60%)
- Splenomegaly rare (2-5%) but seen in severe systemic strep
- Incubation period averages 2-5 days, with symptoms peaking day 2-3
Symptoms and Clinical Presentation Interpretation
Treatment and Antibiotics
- Penicillin V 250mg BID x10 days eradicates GAS in 89% of strep throat cases
- Amoxicillin 50mg/kg/day divided TID x10 days cures 92-96% pediatric strep
- Cephalexin 25-50mg/kg/day BID x10 days effective in 90% penicillin-allergic patients
- Azithromycin 12mg/kg day 1, then 6mg/kg x4 days succeeds in 92% but resistance rising
- Intramuscular benzathine penicillin G 1.2 million units cures 96% with single dose
- Clindamycin 7mg/kg TID x10 days for carriers, 92% eradication vs penicillin 39%
- Short-course (5-day) cephalosporins like cefuroxime axetil 90% bacteriologic cure
- Penicillin failure rate 10-20% due to beta-lactamase producers in co-pathogens
- Amoxicillin-clavulanate 45mg/kg/day BID x10 days overcomes resistance in 95%
- Levofloxacin 500mg daily x10 days for adults, 94% success in resistant cases
- Tonsillectomy reduces strep episodes from 7 to 0.7 per year in recurrent cases
- Analgesics like ibuprofen 10mg/kg reduce fever duration by 24 hours
- Once-daily amoxicillin 50mg/kg eradicates 96%, compliance better than TID
- Clarithromycin 15mg/kg/day x10 days 90% effective alternative
- Adjunctive steroids (dexamethasone 0.6mg/kg) reduce pain by 8-12 hours
- Benzathine penicillin relapse <2% vs oral 10%
- Erythromycin estolate 40mg/kg/day cures 87-92%, GI side effects 25%
- Cefdinir 14mg/kg/day x5-10 days 92% success in short course
- Probiotics with antibiotics reduce diarrhea by 60%
- Compliance with 10-day penicillin 50%, linked to 85% cure if adhered
- Dual therapy penicillin + rifampin 96% eradicates carriers
- Acetaminophen 15mg/kg q6h controls fever in 90%
- Telithromycin 800mg daily x5 days 94.5% bacteriologic success
- Gargling reduces symptom duration by 1.5 days
- Macrolide resistance in GAS 5-10% US, higher in Europe 20%, affects treatment
- Hydration and humidified air shorten recovery by 12-24 hours
- Post-strep follow-up culture negative in 90% treated appropriately
Treatment and Antibiotics Interpretation
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