WHO diagnostic criteria for severe and critical level COVID-19 infection10
| Severe disease (13.8% of population) | Critical disease (6.1% of population) |
| Dyspnoea | Requiring mechanical ventilation |
| Respiratory frequency ≥30/min | Septic shock |
| Blood oxygen saturation ≤93% | Multiple organ dysfunction/failure |
| PaO2/FiO2 ratio <300 | |
| Lung infiltrates >50% of the lung field within 24–48 hours |