Table 1 7-category ordinal scale of clinical status of hospitalized influenza patients

1: Not hospitalized with resumption of normal activities.

2: Not hospitalized, but unable to resume normal activities

3: Hospitalization, not requiring supplemental oxygen

4: Hospitalization, requiring supplemental oxygen

5: Hospitalization, requiring nasal high-flow oxygen therapy and/or noninvasive mechanical ventilation

6: Hospitalization, requiring extracorporeal membrane oxygenation and/or invasive mechanical ventilation

7: Death