Clinical predictors of severe and fatal respiratory syncytial virus infection in adults and the elderly: A retrospective cohort study

Background Respiratory syncytial virus (RSV) is increasingly recognized as a cause of severe respiratory illness in adults, especially the elderly and those with comorbidities. However, data on outcomes and risk factors for severe disease in this population remain limited. Methods We retrospectively analyzed 123 adult patients diagnosed with RSV infection at a tertiary center in Taiwan from 2015 to 2023. Clinical characteristics, laboratory data, detection of other pathogens, clinical course and outcome were reviewed. Multivariable logistic regression identified risk factors for severe RSV infection, including ICU admission and 30-day mortality. Results The mean age was 55.7 years; 50% were aged ≥60 years and 13% were ≥75 years. ICU admission occurred in 17%, with significant associations to viral coinfection and elevated C-reactive protein (CRP). Thirty-day mortality was 13%, and overall in-hospital mortality was 18%, all among patients with comorbidities. Independent predictors of 30-day mortality included late elderly (aOR 24.2, p = 0.03), high CRP > 11.5 mg/dL (aOR 16.4, p = 0.005) and thrombocytopenia < 34,10 3 /μL (aOR 11.4, p = 0.01). Conclusion Advanced age (≥75 years), high CRP, and severe thrombocytopenia are key predictors of mortality in adults RSV patients. These findings highlight the need for targeted prevention strategies, including vaccination, in high-risk populations.