Clinical disease and viral load in children infected with respiratory syncytial virus or human metapneumovirus.

The relationship between respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) quantity in respiratory secretions and severity of illness in children remains unclear. We assessed the effect of hMPV and RSV viral load as determined by reverse transcriptase polymerase chain reaction on disease characteristics. Data were abstracted from medical records of 418 children with RSV and 81 children with hMPV; associations were evaluated in multivariate analyses, both continuously and comparing lower versus higher viral loads. Increasing viral load in hMPV-infected children was associated with increases in presence of fever, bronchodilator use, obtaining chest radiograph, and length of hospital stay. Increasing viral load in RSV-infected children was associated with decreases in inpatient admissions, use of antibiotics, and respiratory rate. Our study has described a significant relationship between viral load and markers of disease severity for both RSV and hMPV in a large population of children evaluated for respiratory disease.