Respiratory syncytial virus hospitalization in middle-aged and older adults

Background: The importance of Respiratory Syncytial Virus (RSV) is increasingly recognized in hospitalized adults, but mainly in those >= 65 years. Objectives: We sought to describe the epidemiology and clinical severity of RSV compared to influenza in hospitalized adults >= 18 years. Study design: Adults hospitalized with acute respiratory illnesses (ARI) of >= 10 days duration were prospectively enrolled from two Michigan hospitals during two influenza seasons. Collected specimens were tested for RSV and influenza by real-time, reverse transcription polymerase chain reaction (RT-PCR). Viral load and subtype were determined for RSV-positive specimens. We evaluated factors associated with RSV and outcomes of infection using multivariable logistic regression. RSV-positive patients were separately compared to two reference groups: RSV-negative and influenza-negative, and influenza-positive patients. Results: RSV was detected in 84 (7%) of 1259 hospitalized individuals (55 RSV-B, 29 RSV-A). The highest prevalence was found in 50-64 year olds (40/460; 8.7%); 98% of RSV cases in this age group had at least one chronic comorbidity. RSV detection was associated with obesity (OR: 1.71 95% CI: 0.99-3.06, p=0.03). Individuals with RSV were admitted to the hospital later in their illness and had a higher median Charlson comborbidity index (3 vs 2 p < 0.001) compared to those with influenza. Clinical severity of RSV-associated hospitalizations was similar to influenza-associated hospitalizations. Discussion: In this study we observed the highest frequency of RSV-associated hospitalizations among adult 50-64 years old; many of whom had chronic comorbidities. Our results suggest the potential benefit of including these individuals in future RSV vaccination strategies.