A comparison of clinical characteristics and mortality in hospitalised patients with respiratory syncytial virus and influenza virus infections: a cohort study

RSV infections remain less well described than influenza infections. We compared symptoms, clinical characteristics and mortality in patients admitted with acute respiratory tract infections due to RSV and influenza virus. We retrospectively collected data from the medical records of adult patients admitted to Akershus University Hospital with a positive PCR for RSV and influenza virus (H3N2, H1N1, and influenza B) from January 1, 2012 to December 31, 2021. We compared demographics, symptoms, and clinical characteristics, and assessed 30-day all-cause mortality using the Kaplan-Meier estimator and logistic regression. We included 2084 (72.7%) patients with influenza and 784 (27.3%) with RSV. RSV patients were older and more comorbid. Sputum production and dyspnoea were more frequently reported by RSV patients, whereas myalgia, headache, fever, sore throat, and gastrointestinal symptoms were more frequently reported by influenza patients. Fever on admission was more common in patients with influenza, whereas RSV patients more often presented with wheezing, higher white blood cell count, and more radiographic evidence of infection. RSV patients were more likely to require respiratory support, admission to higher levels of care, had longer hospital stays, and higher readmission rates. We observed no significant difference in 30-day mortality (adjusted odds ratio 0.93, 95% CI 0.64–1.33). RSV and influenza are mostly clinically indistinguishable on admission, but fever is more frequent in influenza patients. RSV is associated with high utilisation of health care resources and a mortality risk comparable to influenza, highlighting the need for increased awareness and knowledge of RSV.