Background: Influenza remains a common cause of morbidity and mortality worldwide, and viral subtype-related differences in disease outcomes have been documented.
Objective: To characterize the survival experience of adult inpatients with influenza virus-associated pneumonia by viral subtype during five consecutive flu seasons.
Method: We performed a retrospective cohort study; data from 4,678 adults were analyzed using the Kaplan-Meier method. A multivariate Cox proportional hazard regression model was fitted.
Results: The overall in-hospital mortality rate was 25.0 per 1,000 hospital days. The survival probabilities from pneumonia patients went from 93.4% (95% CI 92.6-94.1%) by day three to 43.3% (95% CI 39.2-47.4%) by day 30 from hospital admission. In general, the lowest survival rates were observed in patients with AH1N1 infection. In multiple models, after adjusting for comorbidities and when compared with A non-subtyped virus, pneumonia patients with AH3N2 or B strains had a significantly decreased risk of a non-favorable disease outcome. The association of other strains was not significant.
Conclusions: Our findings suggest that the survival of inpatients with influenza virus-associated pneumonia varies according to the pathogenic viral subtype; the lowest survival rates were observed in patients with AH1N1 infection. This effect was independent of the patients’ gender, age, and the analyzed underlying health conditions.
【저자키워드】 Pneumonia, viral, survival rate., proportional hazards models, Inpatients, Influenza, Human,