Figure 3. The World Health Organization Ordinal Scale for Clinical Improvement (for COVID-19). 0: no clinical or virological evidence of infection; 1: no limitation of activities; 2: limitation of activities; 3: hospitalized, no oxygen therapy; 4: oxygen by mask or nasal prongs; 5: noninvasive ventilation or high-flow oxygen; 6: intubation and mechanical ventilation; 7: ventilation + additional organ support (vasopressors, renal replacement therapy, or ECMO); and 8: death.
