Clinical phenotypes of SARS-CoV-2 disease
| Type | Proportion | Clinical features |
| 1 | 80–85% of symptomatic patients | Fever, headache, mild respiratory symptoms, sore throat, no hypoxaemia, normal chest radiograph, excellent prognosis |
| 2 | ∼80% of hospitalised patients | Mild hypoxia, minor (usually bilateral) infiltrates on chest radiograph, up to 15% may progress quickly to type 3 |
| 3 | ∼15% of hospitalised patients | Moderate to severe hypoxaemia and tachypnoea, high IL-6 and other inflammatory markers May progress to types 4 or 5 |
| 4 | ∼2/3 of patients needing mechanical ventilation | Severe hypoxaemia requiring mechanical ventilation, normal lung compliance, good response to nitric oxide, prone position of little benefit, tidal volume >6 mL·kg−1 allowed, respiratory rate <20 beats·min−1, PEEP <10 cmH2O |
| 5 | ∼1/3 of patients needing mechanical ventilation | High procalcitonin may be increased if mechanical ventilation is delayed in severely hypoxaemic patients, more in keeping with classical ARDS Protective ventilatory strategy and prone position indicated |
SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; IL-6: interleukin-6; PEEP: positive end-expiratory pressure; ARDS: acute respiratory distress syndrome.