Clinical features of respiratory syncytial virus and influenza infections in hospitalized adults across three Italian regions

Acute respiratory infections (ARIs) are important causes of morbidity and mortality globally. Respiratory syncytial virus (RSV) is a highly transmissible viral pathogen that is associated with ARIs, with both RSV and influenza virus infections being leading causes of hospitalization in older (especially frail) individuals. However, prospectively collected data on the incidence of RSV infection are scarce. This prospective study sought to estimate the prevalence of and characterize RSV and influenza virus infection in hospitalized patients. Adult patients (≥18 years of age) who were admitted to the respiratory ward of three major hospitals in northern Italy were included in the study and, therefore, had a nasal swab and underwent routine clinical, laboratory, and imaging testing. The primary objective was to estimate the prevalence of influenza virus and RSV infection in these patients. A total of 246 patients were recruited, 36 of whom had a viral or bacterial respiratory infection. Of these, 9 (3.7% of the total included patients or 25.0% of those with any infection) tested positive for the influenza virus, 5 (55.6%) of whom developed acute respiratory failure, with one dying by 3 months post-discharge. A further 3 patients (1.2% of the total included patients or 8.3% of those with any infection) tested positive for RSV. The three patients with RSV had a greater level of dyspnea and greater severity than those with any infection, and all had pneumonia and developed acute respiratory failure, with one dying during hospitalization. Influenza and RSV infections were identified in patients hospitalized in respiratory wards in Northern Italy. The severe nature of the disease in these patients, including a high rate of pneumonia, emphasizes the importance of preventative measures to protect this vulnerable population and, in particular, vaccination.