['Human bocavirus 1 (HBoV1) has recently been detected in children with respiratory tract infections (RTI). In order to study whether HBoV1 can cause RTI, we investigated its presence in children with upper RTI (URTI), lower RTI (LRTI) and a control group of children without RTI.', 'Nasopharyngeal aspirates (NPA) and blood samples were collected from children admitted to hospital with RTI from 6 June 2007 to 28 February 2009 (n=1154), and from children admitted for elective surgery who had no RTI (n=162). Using polymerase chain reaction (PCR), the NPAs were examined for 17 infectious agents including HBoV1. Blood samples were tested with HBoV1-PCR only.', 'HBoV1 was detected in NPAs from 10% of patients and 17% of controls. Adjusted for age, gender and the presence of other viruses, HBoV1 was not associated with RTI. In the HBoV1-positive NPAs, at least one other virus was detected in 75% and the virus appeared alone in 25%. Adjusted for age and gender, the detection of HBoV1 as the sole virus was associated with RTI, but not with LRTI. Viraemia was found only in children with RTI. The study showed that it was associated with RTI and LRTI. A high HBoV1-load was associated with LRTI, but not with RTI. No interactions between HBoV1 and other infectious agents were found.'] Are human bocavirus in children : mono-detection , high viral load and viraemia associated with respiratory tract infection?