Mild

Mild clinical manifestation

None Imaging Performance

Moderate

Fever, respiratory symptoms, pneumonia performance on X-ray or CT

Severe

Meet any of the followings:

1. Respiratory distress, RR ≥ 30/min;

2. Oxygen saturation ≤ 93% at rest state;

3. Arterial partial pressure of oxygen (PaO₂)/Fraction of inspiration O₂ (FiO₂) ≤ 300 mnHg, 1 mmHg = 0.133 kPa

Critically severe

Meet any of the followings:

1. Respiratory failure needs mechanical ventilation;

2. Shock;

3. Combined with other organ failure, patients need ICU monitoring and treatment