Etiology of acute bronchiolitis and the relationship with meteorological conditions in hospitalized infants in China

BACKGROUND/PURPOSE: To investigate the prevalence of common viruses and Mycoplasma pneumoniae (MP) in hospitalized infants with acute bronchiolitis and study the relationship between bronchiolitis and meteorological conditions. METHODS: A 2-year prospective study was conducted on infants with a first episode of bronchiolitis admitted to Respiratory Department of Suzhou Children's Hospital. Demographic and clinical characteristics and meteorological conditions were obtained and analyzed. RESULTS: Pathogens were identified in 59.6% of 998 cases analyzed. The most frequent pathogen identified was respiratory syncytial virus (28.7%), followed by human bocavirus (11.6%), MP (9.0%), human parainfluenza virus-3 (7.8%), human metapneumovirus (6.6%), influenza A (3.5%), adenovirus (1.0%), and human parainfluenza virus-1 (0.3%). The clinical scores in children with MP or human metapneumovirus single infections, based on the assessment of severity of acute bronchiolitis, were significantly lower than in children with respiratory syncytial virus single infections. Respiratory syncytial virus had the strongest inverse correlation with mean temperature, followed by influenza A and human metapneumovirus. In addition, MP and human parainfluenza virus-3 showed positive correlations with mean temperature. CONCLUSION: Although respiratory syncytial virus was the most frequent pathogen in patients in whom bronchiolitis was diagnosed, other pathogens, including newly identified viruses and MP, also play important roles in infants with bronchiolitis. Different respiratory pathogens have different traits in response to certain meteorological conditions.