Patient state according to WHO clinical progression scale
| Patient state | Clinical characteristics | Severity score |
| Uninfected | Uninfected, no viral RNA detected | 0 |
| Ambulatory mild disease | Asymptomatic, viral RNA detected | 1 |
| Symptomatic, independent | 2 | |
| Symptomatic, assistance needed | 3 | |
| Hospitalised, moderate disease | Hospitalised, no oxygen therapy | 4 |
| Hospitalised, oxygen by mask or nasal prongs | 5 | |
| Hospitalised, severe disease | Hospitalised, oxygen by non-invasive ventilation (NIV) or high flow | 6 |
| Intubation and mechanical ventilation, pO2/FiO2≥150 or SpO2/FiO2≥200 | 7 | |
| Mechanical ventilation, pO2/FiO2<150 (SpO2/FiO2<200) or vasopressors | 8 | |
| Mechanical ventilation, pO2/FiO2<150 and vasopressors, dialysis, or extracorporeal membrane oxygenation (ECMO) | 9 | |
| Dead | Dead | 10 |