Detection and molecular characterization of human group C rotaviruses in Okayama Prefecture, Japan, between 1986 and 2005.

A survey of human group C rotaviruses (CHRVs) was conducted in Okayama Prefecture, Japan, over a period of 19 years between 1986 and 2005. The presence of CHRVs was screened by enzyme-linked immunosorbent assay using CHRV-specific monoclonal antibodies and confirmed by reverse transcription-PCR. Of the 3,722 fecal specimens from sporadic cases of gastroenteritis, 44 specimens (1.2%) were positive for CHRV. The CHRV isolates were detected periodically but continuously, and the rates of positivity changed from one rotavirus season to the next. Moreover, the isolates were mainly detected in April and May, and the mean age of the patients infected with CHRV was 5.27 years. The genome electropherotypes (E types) of the isolates were classified into three patterns, and the dominant pattern changed from year to year. Nucleotide sequences of the VP7 and VP4 genes of 16 strains, which were representatives of 70 isolates from sporadic cases and outbreaks, were determined and analyzed. Although the VP7 and VP4 genes of the strains were closely related to each other, a phylogenetic analysis suggested that each of the VP7 and VP4 genes of the strains were grouped into three genetic lineages. Moreover, the strains could be divided into five types based on the combination of the E type and the genetic lineages of the VP7 and VP4 genes. These results indicate that CHRVs generally exist in Okayama Prefecture and that CHRVs with various genomic backgrounds prevailed in a limited area.