Molecular epidemiology of human rhinovirus C in patients with acute respiratory tract infections in Osaka City, Japan.

Human rhinovirus (HRV) is a causative agent of acute respiratory tract infection (ARTI). In 2007, a novel HRV group, HRV-C, was discovered. This study, which assessed whether HRV-C is epidemic among patients with ARTI, was aimed at analyzing the seasonal prevalence of HRV-C in Osaka City, Japan. Gene amplification tests were performed to detect 10 respiratory viruses in 336 specimens collected during November 2008-October 2009. In total, 364 viruses were detected in 271 specimens. The most commonly detected virus was HRV (n = 84). For HRV-positive specimens, we conducted phylogenetic analyses using the VP4/VP2 gene region to identify the HRV species (HRV-C, 30; HRV-A, 54). Both the number and rate of HRV-C detection were highest in December. The highest numbers and the highest rate of HRV-A detection were obtained in April and June and in April, respectively. Statistical analysis showed that the most probable prevalent period of HRV-C was between September and March, and that of HRV-A was between March and November. These results suggest that HRV-C is mainly epidemic during autumn and early spring; this seasonal prevalence was different from that of HRV-A. Moreover, the HRV-C Osaka strains were scattered in many genetic clusters along with previously reported strains from different parts of the world. This result also emphasizes the worldwide circulation of HRV-C.