Asymptomatic

COVID nucleic acid test positive. Without any clinical symptoms and signs and the chest imaging is normal.

Mild

Symptoms of acute upper respiratory tract infection (fever, fatigue, myalgia, cough, sore throat, runny nose, sneezing) or digestive symptoms (nausea, vomiting, abdominal pain, diarrhea).

Moderate

Pneumonia (frequent fever, cough) with no obvious hypoxemia, chest CT with lesions.

Severe

Pneumonia with hypoxemia (Peripheral oxygen saturation < 92%).

Critical

Acute respiratory distress syndrome (ARDS), may have shock, encephalopathy, myocardial injury, heart failure, coagulation dysfunction and acute kidney injury.