Human Bocavirus in Patients with Respiratory Tract Infection

Background: Human bocavirus (HBoV) is a newly identified viral pathogen, and its clinical epidemiology and significance in respiratory infections have not yet been completely elucidated. We investigated the prevalence of HBoV infection and the association between viral (HBoV) load and clinical features of the infection in patients of all age-groups. Methods: Nasopharyngeal aspirates from patients with symptoms of respiratory infection were tested for presence of HBoV by using real-time polymerase chain reaction. HBoV-positive patients were categorized into low- and high-viral-load groups using 1.0 x 10(6) copies/mL as the threshold value of viral load. Results: Detection rate of HBoV was 4.8% (N=93) in a total of 1,926 samples with peak incidence of infection being observed in patients aged 6-12 months. HBoV infection was more frequently observed in young children, especially, in children aged less than 5 yr, and the HBoV load decreased with increase in age. HBoV was codetected with other respiratory viruses in 17(183%) of the 93 HBoV-positive patients and 15 patients (88.2%) belonged to the low-viral-load group. Patients infected with HBoV alone showed a higher viral load than those patients in whom HBoV was codetected with other respiratory viruses (median load, 3.78 x 10(5) copies/mL vs. 1.94 x 10(4) copies/mL, P = 0.014). Higher pulse rate (P = 0.007) and respiratory rate (P = 0.021) were observed in patients with a high-viral-load. Conclusions: Our results suggest that HBoV may be the causative agent of respiratory infection in the high-viral-load group.