# Comparison of Tomographic Findings in Patients with Influenza A (H1N1) and COVID-19

## TL;DR

This study compares CT scan features of severe pneumonia caused by influenza A (H1N1) and COVID-19 to identify predictors of ventilation and mortality.

## Contribution

The study identifies distinct CT imaging patterns and clinical factors associated with outcomes in severe viral pneumonia caused by H1N1 and COVID-19.

## Key findings

- Ground-glass opacities and consolidation are more common in COVID-19 patients compared to H1N1.
- Pleural effusion is significantly more frequent in H1N1 patients.
- Higher APACHE IV scores and pulmonary damage severity index are linked to increased mortality in COVID-19.

## Abstract

Objectives: The objective of this study was to identify CT-based predictors of mechanical ventilation and mortality in patients with severe and critical viral pneumonia and to examine the association between imaging severity and outcomes in ventilated patients. Methods: We analyzed pulmonary CT scans from 148 patients with severe or critical pneumonia caused by COVID-19 (n = 98) or influenza A H1N1 (n = 50). Patients were assessed based on tomographic patterns, demographics, clinical severity scores (Charlson Comorbidity Index, SOFA, and APACHE IV), and biomarkers. Survival analyses were performed using Kaplan–Meier curves and multivariable Cox regression. Results: Bilateral, peripheral, and basal lung involvement was common across both groups. Ground-glass opacities (89.62%, p ≤ 0.001) and consolidation (61.54%, p = 0.001) were more prevalent in COVID-19, whereas pleural effusion was significantly more frequent in H1N1 (76.92%, p ≤ 0.001). COVID-19 cases more often presented with bilateral (96.94%) and peripheral lesions (77.87%). H1N1 patients were more likely to develop severe ARDS and require mechanical ventilation. In COVID-19, higher APACHE IV scores and pulmonary damage severity index were independently associated with increased mortality. Conclusions: Radiologic and clinical severity profiles differ between COVID-19 and H1N1 pneumonia. CT-based assessments combined with prognostic scores may aid early risk stratification and guide treatment decisions in patients with severe viral pneumonia.