Rhinovirus load and disease severity in children with lower respiratory tract infections.

It has not been clarified if there is a correlation between rhinovirus (RV) load and disease severity in the lower respiratory tract infections of hospitalized children. This study was undertaken to elucidate the contribution of the viral load to the development of disease severity in 412 children ≤3 years of age who were hospitalized with lower respiratory tract infections. The RV load in nasopharyngeal aspirates obtained from the patients at the time of admission was measured by real-time quantitative reverse-transcription polymerase chain reaction (PCR), and the clinical symptoms of the patients were assessed using a severity scoring system. Of the 412 patients, 43 (10.4%) were diagnosed with RV infections only, and 15 were determined to have high severity scores. When all patients infected with RV were assessed, there was no correlation between the viral load and the disease severity. However, there was a significant negative correlation between the disease severity and age among children <11 months of age (n = 15, ρ = -0.677, P = 0.006) and a significant positive correlation between the viral load and the disease severity among children ≥11 months of age (n = 28, ρ = 0.407, P = 0.032). Among the patients infected with RV <11 months of age, the disease severity may be associated with an immature immune response and the small diameter of their airways rather than viral load. By contrast, in the patients ≥11 months of age, viral load may contribute to the development of disease severity.