Table 2. COVID-19 disease severity[3].

Mild disease		Symptomatic patients meeting the case definition for COVID-19 without evidence of viral pneumonia or hypoxia.
Moderate disease	Pneumonia[73]	Adolescent or adult with clinical signs of pneumonia (fever, cough, dyspnea, fast breathing) but no signs of severe pneumonia, including SpO2>90% on room air.
Severe disease	Severe pneumonia[73]	Adolescent or adult with clinical signs of pneumonia (fever, cough, dyspnea, fast breathing) plus one of the following: respiratory rate >30 breaths/min; severe respiratory distress; or SpO2 <90% on room air.
Critical disease	Acute respiratory distress (ARDS)[74-76]	syndrome Onset: Within one week of a known clinical insult (i.e. pneumonia) or new or worsening respiratory symptoms. Chest imaging: (radiograph, CT scan, or lung ultrasound): Bilateral opacities, not fully explained by volume overload, lobar or lung collapse, or nodules. Origin of pulmonary infiltrates: Respiratory failure not fully explained by cardiac failure or fluid overload. Need objective assessment (e.g. echocardiography) to exclude hydrostatic cause of infiltrates/edema if no risk factor present. Oxygenation impairment in adults: 200 mmHg <PaO2/FiO2a <300 mmHg (with PEEP or CPAP >5 cmH2O).b
Critical disease	Sepsis[77,78]	Adults: Acute life-threatening organ dysfunction caused by a dysregulated host response to suspected or proven infection. Signs of organ dysfunction include: altered mental status, difficult or fast breathing, low oxygen saturation, reduced urine output, fast heart rate, weak pulse, cold extremities or low blood pressure, skin mottling, laboratory evidence of coagulopathy, thrombocytopenia, acidosis, high lactate, or hyperbilirubinemia.
	Septic shock[77,78]	Adults: Persistent hypotension despite volume resuscitation, requiring vasopressors to maintain MAP >65 mmHg and serum lactate level >2 mmol/L.
See the WHO website for most up-to-date case definitions.][79] SpO2: Pulse oxygen saturation; CT: Computed tomography; PaO2: Partial pressure arterial oxygen; FiO2: Fraction of inspired oxygen; PEEP: Positive end-expiratory pressure; CPAP: Continuous positive airway pressure; MAP: Mean arterial pressure; a: If altitude is higher than 1000 m, then the correction factor should be calculated as follows: PaO2/ FiO2 ¥ barometric pressure/760; b: When PaO2 is not available, SpO2/FiO2 <315 suggests ARDS (including in non-ventilated patients).