The interdependence between rhinovirus cycle threshold values, viral co-detections, and clinical disease severity in children with and without comorbidities

Rhinoviruses (RVs) are a leading cause of acute respiratory infections (ARI) in children. The relationship between RV viral loads (VL), RV/viral-co-detections and disease severity, is incompletely understood. We studied children and adolescents ≤21 years with RV-ARI that were identified as inpatients or outpatients using a PCR panel from 2011-2013. RV VL were stratified according to cycle threshold (CT) values in high (≤25), intermediate (26-32) and low (>32). Adjusted analyses were performed to assess the role RV VL and RV/viral codetections on hospital admission, oxygen requirement, PICU care, and length of stay. Of 1,899 children with RV-ARI, 78% had chronic comorbidities and 24% RV/viral co-detections. Single RV vs RV/viral co-detections was associated with higher VL (24.74 vs 26.62 CT; p = 0.001) and older age (14.9 vs 9.5 months; p = 0.0001). Frequency of RV/viral co-detections were inversely proportional to RV loads: 32% with low; 28% with intermediate, and 19% with high VL, p = 0.0001. Underlying conditions were independently associated with all clinical outcomes, high VL with PICU care, and single RV-ARI with higher odds of hospitalization. In summary, single RV vs RV/viral co-detections were associated with higher VL and older age. Underlying diseases, rather than RV loads or RV/viral co-detections, consistently predicted worse clinical outcomes.