Infection with multiple viruses is not associated with increased disease severity in children with bronchiolitis

Background The clinical relevance of parallel detection of multiple viruses by real‐time polymerase chain reaction (RT‐PCR) remains unclear. This study evaluated the association between the detection of multiple viruses by RT‐PCR and disease severity in children with bronchiolitis. Methods Children less than 2 years of age with clinical symptoms of bronchiolitis were prospectively included during three winter seasons. Patients were categorized in three groups based on disease severity; mild (no supportive treatment), moderate (supplemental oxygen and/or nasogastric feeding), and severe (mechanical ventilation). Multiplex RT‐PCR of 15 respiratory viruses was performed on nasopharyngeal aspirates. Results In total, 142 samples were obtained. Respiratory Syncytial virus (RSV) was the most commonly detected virus (73%) followed by rhinovirus (RV) (30%). In 58 samples (41%) more than one virus was detected, of which 41% was a dual infection with RSV and RV. In RSV infected children younger than 3 months, disease severity was not associated with the number of detected viruses. Remarkably, in children older than 3 months we found an association between more severe disease and RSV mono‐infections. Conclusion Disease severity in children with bronchiolitis is not associated with infection by multiple viruses. We conclude that other factors, such as age, contribute to disease severity to a larger extent. Pediatr Pulmonol. 2012; 47:393–400. © 2011 Wiley Periodicals, Inc.