High incidence of respiratory viruses in critically ill children

Background: Acute lower respiratory tract illness is a major cause of hospitalization, respiratory failure, and death in children worldwide. However, infectious agents are not identified in >50% of these clinical illnesses using traditional methods such as rapid antigen detection assays or viral culture. Objective: To conduct a pilot study using RT-PCR to determine the frequency of respiratory viruses in critically ill children with respiratory compromise. Methods: Critically ill children admitted to the Pediatric Critical Care Unit during 2 winter seasons with respiratory compromise or failure were prospectively enrolled. Respiratory tract specimens (tracheal lavage or nasal wash) were tested for 11 different viruses using realtime RT-PCR, including respiratory syncytial virus (RSV), human metapneumovirus (HMPV), influenza A (IAV) and B (IBV), parainfluenza viruses (PIV) 1-3, coronaviruses OC43, 229E, and Netherlands, and human rhinovirus (HRV). Results: Thirty-two children were enrolled, 28 (88%) of which required mechanical ventilation. Clinical diagnoses included bronchiolitis, croup, asthma, apnea, and pneumonia. Of these patients, 28/32 (88%) tested positive for one of eleven viruses by RT-PCR. Compared to antigen testing for RSV, IAV, and IBV, RT-PCR detected an additional nine infections for an increased yield of 53%. RT-PCR also detected coronavirus infections in five patients, including three patients with Netherlands coronavirus. Co-infection with more than one virus was detected in 8/32 (25%). None of the 32 patients tested positive for HMPV, PIV 1, or PIV 3. Conclusions: We detected a respiratory virus in 88% of children with respiratory failure. RT-PCR significantly increased the identification of viruses compared to antigen testing. RSV, influenza A, and coronaviruses were the most common viruses detected. Our data suggest that a viral etiology can be identified in the majority of childhood episodes of severe respiratory disease and that RT-PCR is a useful addition to the diagnostic approach.