Genotyping of mumps virus detected in Yokohama City from 1999 to 2010

A survey of mumps infections from 1999 to 2010 was conducted in Yokohama City, Japan, and 17 cases--including 4 cases of aseptic meningitis--were positive for mumps virus (MuV). Based on the phylogenetic analysis of the small hydrophobic gene of the MuV genome, 3, 2, and 12 of the isolates were classified into genotypes B, L, and G, respectively. The results were supported by phylogenetic analysis of hemagglutinin-neuraminidase genes. The 3 isolates of genotype B, obtained in 2000, 2004, and 2007, were closely related to indigenous lineages and vaccine strains in Japan. Two isolates obtained from 1999 to 2000 were assigned to genotype L. Twelve isolates obtained from 2000 to 2010 were classified into genotype G, in which 8 isolates obtained from 2000 to 2006 and 4 isolates obtained in 2010 were closely related to MuVi/Gloucester.GBR/32.96 and MuVi/London.GBR/0.03, respectively. Precise analyses of nucleotide sequences suggested that the 4 viruses isolated in 2010 were not directly derived from the evolution of MuV existing before 2006 in the Yokohama area.