Distinctive clinical features of human bocavirus in children younger than 2years

Background and objective: Clinical characteristics of human bocavirus (HBoV) infection have been studied worldwide, but their importance of those characteristics remains unknown. We investigated distinctive clinical features of HBoV-positive children with lower respiratory tract infection (LRTI). Methods and results: During April 2007-July 2009, for 402 hospitalized children younger than 2years with LRTI, we prospectively examined virus genomes in nasopharyngeal swabs for HBoV, respiratory syncytial virus (RSV), rhinovirus, metapneumovirus, parainfluenzavirus, and adenovirus. The HBoV genomes were identified in 34 patients (8.5%). Clinical and laboratory data of HBoV-positive and other virus/bacteria-negative patients (n=18) were analyzed and compared with data of RSV-single positive patients (n=99). The seasonal distribution of HBoV exhibits a concentration of cases during March-September, with most RSV cases occurring during winter in Japan. The minimum age of HBoV-positive patients was 5months, although 44 patients (44%) with RSV were younger than 6months. The main clinical features were respiratory distress and hypoxia. Hypoxia advances within 3days after onset. The mean oxygen saturation on arrival was 92.8%, which was significantly lower than that in patients with RSV (p