Detection and quantitative analysis of human bocavirus associated with respiratory tract infection in Osaka City, Japan.

HBoV was initially identified in patients with RTI in 2005. Since its discovery, there have been continual reports concerning HBoV detection and its prevalence. In this study of clinical specimens from young children, real-time PCR was undertaken to examine whether HBoV infection is associated with RTI and to support quantitative analysis of HBoV in these patients. In all, 376 specimens were collected from patients with RTI during April 2006-October 2008. Analyses revealed HBoV in 59 specimens (15.7%). Of HBoV-positive patients, children under the age of 3 years comprised 94.9%. Of the HBoV-positive samples, 47.5% were codetected with other respiratory viruses (dual infection, 27; triple infection, 1). During the study period, the numbers and rate of detection of HBoV were high mainly around May. Statistical analyses showed that the detection rate of HBoV during April-June was higher than during other months. Moreover, the viral load was greater in subjects with infection with HBoV alone than in subjects with mixed respiratory viral infections. Considering these results together, HBoV is probably associated with RTI in young children. However, the pathogenesis of this infection and the importance of the high rate of co-infection remain uncertain. Additional epidemiologic information and further analyses are necessary to clarify the virological characteristics and the linkage of HBoV to disease.