Abstract
Background. Adults hospitalized with acute respiratory infections, including respiratory syncytial virus (RSV), often have multiple underlying conditions. Few data are available on the combined effect of conditions on risk of severe outcomes from RSV disease. Methods. We enrolled adults hospitalized with RSV at 26 hospitals in 20 US states admitted January 2022-July 2024. Seventeen underlying conditions were selected after excluding those with rare prevalence (<= 1%) or high pairwise correlation (>= 0.7). We applied Bayesian profile regression to identify profiles of conditions associated with increased risk of RSV severe outcomes, stratifying among adults aged 18-59 and >= 60 years. Results. We analyzed data from 1111 adults hospitalized with RSV (median [IQR] age, 66 [53-75] years). Among 397 adults aged 18-59 years, 2 profiles were identified: (1) minimal prevalence with fewer underlying conditions and a posterior median intensive care unit (ICU) admission risk of 21% (95% credible interval, 16%-25%) and (2) cardiorenal/diabetes with frequent heart failure, chronic kidney disease, diabetes, and increased ICU admission risk (37% [27%-48%]). Among 714 adults aged 60 years and older, 4 profiles were identified: (1) minimal prevalence (ICU admission risk, 22% [18%-26%]), (2) cardiorenal/diabetes (27% [21%-34%]), (3) hematologic malignancy and transplant receipt (12% [6%-21%]), and (4) chronic pulmonary disease with home oxygen dependence (44% [25%-66%]). Conclusions. Distinct underlying condition profiles with varying risks of critical illness were observed among inpatients with RSV. These findings could support recognition of high-risk patients to inform RSV prevention strategies and suggest that the role of multimorbidity in severe RSV disease risk warrants further attention.