WU polyomavirus detected in respiratory tract specimens from young children in Japan.

Polyomaviruses (PyV) WU and KI are reportedly associated with respiratory tract disease (RTD) worldwide but their incidence is unclear in Japan. In a 2 year prospective study, WU/KIPyV were detected in 48 (13.9%) and in five (1.4%) of 345 children hospitalized with lower RTD, respectively. The seasonal distribution was observed in spring and early summer. Other respiratory viruses were co-detected in 51% of PyV-positive patients, but eight (2.3%) of the WUPyV-positive patients were negative for other known pathogens.