Multivariate analysis of the severity of respiratory features using a proportional odds model.

*Grouping of patients was based on the number of days from symptom onset to oseltamivir administration: Group 1, ≤2 days; Group 2, 3–7 days; Group 3, 8–14 days; Group 4, >14 days.†The odds ratio of socioeconomic level was presented when the level was upped by one unit as a continuous variable.‡AGE 1 (age §Comorbidities are compared between present and absent.χ2: Chi-square test.