Comparison between clinical outcomes in influenza A and B Infections: A multicenter retrospective cohort study

Abstract

Objectives: Influenza significantly contributes to seasonal morbidity and strains healthcare resources, yet data directly comparing types A and B remain limited. This study assesses potential differences in clinical severity and outcomes between these two influenza types. Methods: We conducted a multicenter retrospective study of adult patients diagnosed with either influenza A or B. Using logistic regression, we identified predictors of adverse outcomes across demographics, comorbidities, and clinical parameters. Results: The influenza A and B cohorts included 234 and 113 patients, respectively. In comparison to influenza B, influenza A patients were more likely to receive oseltamivir (43.5% vs 27.9%, p = 0.01) and showed similar rates of radiological abnormalities (27.8% vs 24.8%, p = 0.6). Age ≥65 years remained the strongest predictor of hospitalization (aOR 4.78, p = 0.01). Predictors of ICU admission included age<65 (aOR 3.18, p = 0.02), radiological bilateral involvement (aOR 19.4, p < 0.001), receiving oseltamivir treatment (aOR 2.43, p = 0.01) with a trend towards documented superinfection (aOR 2.56, p = 0.07). Short-term favorable outcomes were more common in influenza B (aOR 2.52, p = 0.02), whereas chronic respiratory disease and Charlson comorbidity index reduced likelihood of favorable outcomes (aOR 0.34, p = 0.04 and 0.25, p = 0.001, respectively). Kaplan-Meier survival curves revealed similar mortality rates at 90 days between influenza A and B types (13.4% vs 8.7%, p = 0.3). Conclusion: Influenza type A and B exhibit distinct clinical trajectories and influenza B should not be neglected. These findings underscore the need for earlier diagnosis testing to promote earlier antiviral initiation and broader vaccination policies tailored to both influenza types.

Keywords

• Outcome
• Influenza B
• Respiratory tract infections
• Influenza
• Mortality