I. Isolation of group A streptococci (Streptococcus pyogenes)
II. Clinical signs of severity
A. Hypotension: systolic blood pressure ≤ 90 mm Hg in adults or below fifth percentile for age in children
And
B. Two or more of the following signs:
1. Renal impairment: creatinine ≥ 177 μmol/L (≥2 mg/dL) for adults or ≥2× the upper limit of normal
2. Coagulopathy: platelets ≤ 100 × 109/L or evidence of DIC
3. Liver involvement: serum AST, ALT, or Bilirubin levels ≥2× the upper limit of normal
4. Adult respiratory distress syndrome
5. A generalised erythematous macular rash that may desquamate
6. Soft tissue necrosis, including necrotizing fasciitis or myositis, or gangrene
