We studied the evolution of the G gene in the new genotype ON1 of RSV detected from patients with acute respiratory infection in Japan. Phylogenetic analyses and the evolutionary timescale were obtained by the Bayesian MCMC method. We also analyzed p-distance and positive selection sites. A new genotype ON1 emerged around 2001. The evolution rate was rapid (3.57 Â 10 À3 substitutions/site per year). The p-distance was short and no positive selection site was found in the present strains. These results suggested that a new genotype ON1 of RSV-A emerged approximately10 years ago and spread to some countries with a high evolution rate.

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Detailed genetic analysis was carried out of the VP4/VP2 coding region in human rhinovirus species C (HRV-C) strains detected in patients with acute respiratory infection in Japan. Phylogenetic trees were constructed by the neighbour-joining (NJ) and maximum-likelihood (ML) methods. The NJ phylogenetic tree assigned 11 genotypes to the present strains, whilst the ML tree showed that the strains diversified sometime in the early 1870s. Moreover, the pairwise distance among the present strains was relatively long, and the rate of molecular evolution of the coding region was rapid (3.07¾10 "3 substitutions per site per year). The results suggest that the present HRV-C strains have a wide genetic divergence and a unique evolutionary timescale.