1-INTRODUCTION
Viral lower respiratory tract infection (LRTI) presents with an acute, self-limiting, and uncomplicated infection in healthy children, with a significant cause of public health problems and health care costs in those with any known risk factor1. In the United States (US), pneumonia and bronchiolitis, generally associated with viral agents, are the most common causes of LRTI-associated hospitalizations in children under five years2. Moreover, between 2002-2009, the estimated hospital charges for children with bronchiolitis younger than two years of age increased from 1.3 to 1.7 billion3.
With the advances in molecular technology, multiple viruses have been determined at a rate of 30-70% in children hospitalized with LRTI4,5. However, the clinical implications of viral coinfection remain unclear and controversial reports have been published. While Richard et al.6 found that infants with the dual respiratory virus were 2.7 times higher at risk of admission to the intensive care unit (ICU) than those with single-virus infection, Brand et al.7 showed no increased risk of severe bronchiolitis in infants with multiple viruses. Despite the small sample size, our previously published study suggested that the presence of influenza A and human bocavirus (HBoV) coinfection were independently a risk for invasive mechanical ventilation (IMV) support8. Some meta-analyses showed a comparable effect on hospital admission, the length of hospital stay, and oxygen requirements or death between children with a single virus and viral coinfection5,9. In contrast, a systemic review determined that further research has needed to clarify the impact of viral coinfection on the severity of LRTI because of conflicting results in studies10.
Considering these controversial reports, we conducted an observational study to investigate the effect of virus coinfection on LRTI in hospitalized children under five years of age. These findings may identify the degree to which clinicians should consider viral coinfection when assessing children’s risk of developing severe illness.