Clinical meaning
Pharyngitis is inflammation of the pharynx, with viral etiologies (rhinovirus, adenovirus, EBV, influenza) accounting for 70-85% of cases and Group A Streptococcus (GAS/S. pyogenes) accounting for 15-30% in children and 5-15% in adults. GAS pharyngitis is significant because untreated infection can trigger post-infectious immunologic complications: acute rheumatic fever (ARF — molecular mimicry between streptococcal M protein and cardiac tissue causing valvulitis) and post-streptococcal glomerulonephritis (PSGN — immune complex deposition in glomeruli). The Centor criteria (modified McIsaac) guide the need for testing: fever > 38°C, tonsillar exudates, tender anterior cervical lymphadenopathy, absence of cough, and age adjustment. A score ≥ 3 warrants rapid antigen detection test (RADT) or throat culture. Antibiotics treat GAS to prevent ARF (antibiotics must be started within 9 days of symptom onset), reduce symptom duration by 1-2 days, and decrease transmission.