In the context of the previous reports of WUPyV detection in Australia and North America (3), our data suggest a worldwide distribution of WUPyV. Most of the WUPyV-positive children were <4 years of age, and WUPyV DNA was rarely found in children >6 years of age. This age distribution is compatible with WUPyV infection occurring in day nurseries and kindergartens. In keeping with the fi ndings of Gaynor et al. (3), we observed a high number of co-infections. The true number of co-infections in our study is probably higher than the reported 53.2% because we did not test for several respiratory pathogens, such as coronaviruses, rhinoviruses, enteroviruses, and the human metapneumovirus. Hypotheses to account for the detection of WUPyV in respiratory samples include the following: WUPyV is a persisting asymptomatic virus that is detected by chance, WUPyV is a persisting virus that is reactivated by an infl ammatory process, or WUPyV is a predisposing or aggravating factor of respiratory diseases. Further studies are necessary to determine whether WUPyV is a human pathogen.