Comparison of clinical characteristics and outcomes in hospitalized adult patients infected with respiratory syncytial virus and influenza virus

Background: Because patients infected with respiratory syncytial virus (RSV) have been reported to be older than patients infected with influenza virus, the more frequent incidence of complications in RSV-infected patients may be age-related. This study compared clinical characteristics and outcomes in hospitalized adults infected with RSV with findings in age- and sex-matched adults infected with influenza virus.

Methods: The medical records of hospitalized adult patients infected with RSV or influenza virus at two university hospitals from 2013 to 2022 were retrospectively analyzed. Virus infection was confirmed by real-time polymerase chain reaction. Each RSV-infected patient was matched by age and sex with two influenza virus-infected patients, and their clinical symptoms, laboratory parameters and hospital courses were compared.

Results: The study cohort consisted of 552 patients, 184 infected with RSV and 368 infected with influenza virus. Fever (71.2% vs. 79.9%, p = .022) and cough (70.1% vs. 80.4%, p = .007) were significantly less frequent in the RSV than in the influenza group, whereas white blood cell counts (9132/mm³ vs. 7616/mm³, p < .001) and C-reactive protein concentrations (10.25 vs. 8.88 mg/dL, p = .029) were significantly higher in the RSV group. The frequency of oxygen therapy was higher (60.3% vs. 48.6%, p = .010) and hospital stay was longer (8 vs. 6 days, p = .003) in RSV than in influenza virus-infected patients.

Conclusions: Clinical symptoms were less frequent, but disease was more severe, in hospitalized adult patients infected with RSV than in age- and sex-matched patients infected with influenza. Greater attention should be paid to diagnosing and preventing RSV infection in adults.