Table 1.

Severity of SARS CoV-2 infection, with typical features.

Severity	Indicators	Estimated prevalence
Asymptomatic	Absence of typical or atypical clinical manifestations; no changes in X-ray and/or CT scans	80%
Mild disease	Fever, cough, sore throat, nausea/vomiting, diarrhea, loss of taste or smell but no dyspnea; normal O2 saturation and usually no changes in X-ray and/or CT scans
Moderate disease	Symptoms of mild disease plus evidence of lower respiratory tract infection (exam and/or imaging (presence of ground-glass opacities and lung consolidation), O2 saturation ≥94% on room air
Severe disease	Symptoms of moderate disease but O2 saturation <94%, PaO2/FiO2 <300 mmHg, respiratory frequency >30 breaths per minute, or chest imaging showed obvious lesion progression more than 50% within 24–48 h	15%
Critical disease	Symptoms of severe disease but intubated with respiratory failure, septic shock, and/or multiorgan dysfunction; ground-glass opacities (usually bilateral), lung consolidation, pulmonary nodules.	5%