GAS (S. pyogenes) causes suppurative infections and is associated with postinfectious syndromes such as acute rheumatic fever (ARF) and poststreptococcal glomerulonephritis (PSGN).

• Up to 20% of people may have asymptomatic pharyngeal colonization with GAS.
  • - Pharyngitis due to GAS is one of the most common bacterial infections of childhood.
  • - GAS accounts for 20-40% of all cases of exudative pharyngitis in children >3 years of age.
• The incidence of all GAS infections is ~10-fold higher in low-income than in high-income countries. Worldwide, GAS contributes to ~500,000 deaths per year.
• The major surface protein (M protein) and the hyaluronic acid polysaccharide capsule protect GAS against phagocytic ingestion and killing.
• GAS makes a large number of extracellular products that may contribute to local and systemic toxicity; these include streptolysins S and O, streptokinase, DNases, and the pyrogenic exotoxins that cause the rash of scarlet fever and contribute to the pathogenesis of toxic shock syndrome (TSS) and necrotizing fasciitis.
• Respiratory droplets provide the usual route of transmission, although other mechanisms have been described.