Table 1.

Clinical characteristics of asymptomatic infections and other types of COVID-19.2, 3

Type	Clinical characteristics	RT-PCR test for COVID-19
Asymptomatic	No clinical symptoms and chest imaging findings.	Positive
Mild	Mild clinical symptoms, such as fever, fatigue, cough, anorexia, malaise, muscle pain, sore throat, dyspnea, nasal congestion, headache. No abnormal chest imaging findings.	Positive
Moderate	Mild or moderate clinical features. Chest imaging showed mild pneumonia manifestation.	Positive
Severe	Suspected respiratory infection symptoms, plus any of the following:  Shortness of breath, RR ≥ 30 breaths/min;  At rest, oxygen saturation ≤93%;  Pa02/Fi02 ≤ 300 mmHg (1 mmHg = 0.133 kPa). Chest imaging showed the lesions significantly progressed > 50% within 24–48 h was a severe disease.	Positive
Critical	Rapid progress of disease, plus any of the following: Respiratory failure, and need mechanical ventilation; Shock; Combined with other organ failure requires ICU monitoring treatment.	Positive

RT-PCR, reverse transcriptase-polymerase chain reaction; RR, respiratory rate; Pa0_2, arterial partial pressure of oxygen; Fi0_2, oxygen concentration; ICU, intensive care unit.