Rhinovirus in Adults With Severe Lower Respiratory Tract Infection: Incidental Carriage or Primary Pathogen? A Comparative Study Across Different Clinical Status Categories.

BACKGROUND: Rhinovirus (RV) is a recognized respiratory pathogen, but its role in severe lower respiratory tract infections (LRTI) in adults remains debated. The aim of the study was to investigate RV in different clinical status categories at Hospital Sao Paulo, a tertiary facility in Sao Paulo, Brazil. METHODS: We conducted a cross-sectional study between January 2023 and August 2025, enrolling 2688 participants: asymptomatic adults (n = 193), adult outpatients with acute respiratory infection (ARI) (n = 1274), hospitalized adults with severe LRTI (n = 809) and hospitalized children with LRTI (n = 412). RV detection was performed by RT-qPCR. RESULTS: RV detection rates were 4.7% in asymptomatic adults, 7.8% in hospitalized adults, 15.6% in adults outpatients and 20.9% in hospitalized children. The detection rate in hospitalized adults was statistically similar to that of asymptomatic adults (ƿ = 0.135), but significantly lower than that of adults outpatients (ƿ < 0.001) and hospitalized children (ƿ < 0.001). Among RV-positive hospitalized adults, 90.5% had underlying comorbidities, with 65.1% presenting immunosuppressive conditions. CONCLUSIONS: In hospitalized adults with LRTI, RV detection rates are comparable to those in asymptomatic individuals, suggesting frequent incidental carriage rather than a primary causal link to severe disease. Conversely, RV is a major pathogen in acute, non-severe community illness in adults and a clearly pathogenic agent in severe LRTI in children.