Coinfections with other viruses are frequently observed in HBoV infections and often occur in more than 50 % of the tested samples [56, 46, 61] . Two recent studies report that the viral load of HBoV was significantly higher in children with monoinfections than in children with coinfections [57, 62] . The high rate of coinfections with other viruses may then be explained by the persistence of HBoV in the respiratory tract. DNA quantification in HBoV positive samples revealed that the viral load of 42.5 % of the positive patients was > 1.0 x 10 5 DNA copies/mL, suggesting that below this cut-off HBoV may be a persistant virus or a bystander [54].