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.