Table 1

Clinical classification of COVID-19 patients [2].

Category	Clinical manifestation
Asymptomatic	SARS-CoV-2 nucleic acid test shows positive. Patients have no clinical symptoms or 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, and chest imaging shows lesions.
Severe	Pneumonia with hypoxemia (oxygen saturation<92%)
Critical	Acute respiratory distress syndrome (ARDS). Patients may have shock, encephalopathy, myocardial injury, heart failure, coagulation dysfunction, and acute kidney injury.