Distribution of COVID-19 patients in China 2020, by symptom severity

Symptoms were categorized as mild, severe or critical as follows:
Mild cases: include all patients without pneumonia or cases of mild pneumonia.
Severe cases: include patients who suffered from shortness of breath, respiratory frequency ≥ 30/minute, blood oxygen saturation ≤93%, PaO2/FiO2 ratio <300,37 and/or lung infiltrates >50% within 24–48 hours.
Critical cases: include patients who suffered respiratory failure, septic shock, and/or multiple organ dysfunction or failure.

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