Table 2 COVID-19 severity classifications across different guidelines harmonized according to WHO’s classification of severity, guided by WHO case definition
WHO classification and case definition | NHC (China) | SIMIT Lombardy section (Italy) | SWAB (Netherlands) | Sciensano (Belgium) |
|---|---|---|---|---|
Mild | “Mild” | “Mild respiratory symptoms” | “Mild” | “Mild to moderate” |
- Uncomplicated upper respiratory tract viral infection | - Mild clinical symptoms - No radiologic signs of pneumonia | - Fever (> 37.5 °C), cough, no dyspnoea | - No supplemental oxygen required | - no oxygen requirement or no evidence of pneumonia |
Pneumonia | “Common” or “Regular” | “Moderate respiratory symptoms” | Nil | |
- Pneumonia but no signs of severe pneumonia - No need for supplemental oxygen | - Fever, symptoms of respiratory tract infection - Signs of pneumonia on imaging | - Fever (> 37.5 °C), cough, mild to moderate dyspnoea, and/or - Pneumonia on chest x-ray - Mild respiratory symptoms in age >70 years and/or co-morbidities with increased mortality risk | ||
Severe | “Severe” | Nil | “Moderately severe” | “Severe” |
- Fever or suspected respiratory infection, plus 1 of the following: • RR > 30/min; • Severe respiratory distress • SpO2 ≤ 93% on room air | - Dyspnoea, respiratory rate > 30/min - SpO2 < 93% at rest, or - PaO2/FiO2 ratio < 300 mmHg | - Requires monitoring in ward - Supplemental oxygen required | ≥1 of the following: - RR ≥30/min - SpO2 ≤ 93% - PaO2/FiO2 ratio < 300 mmHg - Lung infiltrates > 50% of the lung field within 24–48 h | |
Critical | “Critical” | “Critically ill” | “Very severe” | “Critical” |
- ARDS, or - Sepsis with acute organ dysfunction | - Respiratory failure requiring mechanical ventilation, or - Presence of shock, or - Multi-organ failure requiring monitoring in ICU | - ARDS - Respiratory failure - Haemodynamic failure (re-classified under WHO’s “critical” category) | - Monitoring in ICU required, or - ECMO required, or - Clinical deterioration from moderate severity with initial anti-viral therapy | ≥1 of the following: - ARDS - Sepsis - Altered consciousness - Multi-organ failure |