Burden of primary influenza and respiratory syncytial virus pneumonia in hospitalised adults: insights from a 2-year multi-centre cohort study (2017–2018)

Background: Viral community-acquired pneumonia (CAP) is a potentially serious illness, particularly in adult patients with underlying chronic conditions. In addition to the most recent SARS-CoV-2, influenza, and respiratory syncytial virus (RSV) are considered the most relevant causes of viral CAP. Aims: To describe the clinical features of hospitalised adults admitted for influenza-A/B and RSV pneumonia and analyse, according to aetiology, factors associated with non-invasive ventilation (NIV) failure and in-hospital death (IHD). Methods: This was a retrospective and multi-centre study of all adults who were admitted for laboratory-confirmed influenza-A/B or RSV pneumonia, during two consecutive winter seasons (October–April 2017–2018 and 2018–2019) in three tertiary hospitals in Portugal, Italy and Cyprus. Results: A total of 356 adults were included in the study. Influenza-A, influenza-B and RSV were deemed to cause pneumonia in 197 (55.3%), 85 (23.9%) and 74 (20.8%) patients, respectively. Patients with both obstructive sleep apnoea or obesity hypoventilation syndrome and influenza-A virus pneumonia showed a higher risk for NIV failure (odds ratio (OR) 4.66; 95% confidence interval (CI) 1.42–15.30). Patients submitted to NIV showed a higher risk for IHD, regardless of comorbidities (influenza-A OR 3.00; 95% CI 1.35–6.65, influenza-B OR 4.52; 95% CI 1.13–18.01, RSV OR 5.61; 95% CI 1.26–24.93). Conclusion: The increased knowledge of influenza-A/B and RSV pneumonia burden may contribute to a better management of patients with viral CAP.