Severe viral infections requiring intensive care unit admissions- aetiology, co-infections, respiratory interventions and outcomes.

Introduction: Severe viral infections are common in patients requiring admission to intensive care units (ICU). Furthermore, these patients often have additional secondary or co-infections. Despite their prevalence, it remains uncertain to what extent those additional infections contribute to worse outcomes for patients with severe viral infections requiring ICU admission. This study aims to characterise severe viral infections requiring admission to intensive care, and describe their viral aetiology, the incidence of additional infections, and their clinical outcomes.

Methods: This retrospective single-centre cohort included consecutive adults admitted to the intensive care unit (ICU) with a positive polymerase chain reaction (PCR) test for viral infection from 2015 to 2024. Patients with SARS-CoV-2 were not included in this analysis. The data were retrieved from all available electronic databases. Patients were further stratified to compare severe viral infections alone to those with other microbiology confirmed co-infection (within 48 h of admission) and secondary infection (48 h after ICU admission).

Results: We identified 222 with positive PCR for viral infection admitted to ICU. The majority were admitted with radiographic evidence of pneumonia (73.0%). Rhinovirus (28.4%), influenza A (18.5%), and RSV (16.2%) were the most common viral pathogens. Of the total, 149 patients had viral infection alone, 50 had co-infections, and 23 developed secondary infections. 30-day and ICU mortality were similar for viral alone, co-infection and secondary infection groups. Although those with secondary infection had a greater hospital and ICU length of stay, this was not reflected in the duration of mechanical ventilation or 30-day hospital mortality.

Conclusion: In our large cohort of severe viral infections where Rhinovirus was the most common pathogen. This patient population constitute a high burden of respiratory support. The study also characterised 22.5% had co-infection, and 10% had subsequent secondary infection. While patients with secondary infections had prolonged ICU and hospital stay, the 30-day mortality was similar between all groups.