Elucidation of prevalence of group B human rotavirus in Asia

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In the present study, group B rotaviruses were detected in India (9 strains in 4086 specimens), Bangladesh (14 strains in 1151 specimens), and China (2 strains in 769 specimens), mostly in specimens from sporadic diarrheal cases of adult patients. Genetic analysis was done for CAL-1 strin in India, Wh683 strain in China, and four strains (Bang373, Bang544, Bang334, and Bang402) in Bangladesh. The Chinese strain Wh683 which was obtained in Wuhan city in 2000 was genetically extremely closeer (sequence identity was 98-99%) to the ADRV strain (a prototype of human group B rotacirus detected in 1982) than to CAL-1 or Bang373 (identities of 90-95%), indicating that group B rotaviruses in China are highly conserved. In contrast, VP7 gene sequences of the Bangladeshi group B rotaviruses were almost identical each other and showed also high sequence identity to Indian strain CAL-1 (98%) and also to Chinese strain ADRV (92%), while identities to bovine and murine viruses were considerably low (60-63%). Other genes of Bang373 and Bang544 encoding VP2, VP4, VP6, and NSP1〜NSP5 showed also extremely high sequence identities to those of CAL-l (97.7-99.4%) than those of ADRV (89.9-93.9%). Characterization of nucleotide substitutions among Bang373, CAL-1, and ADRV suggested that all the gene segments might have evolved neutrally at similar mutaton rates. In conclusion, group B rotaviruses detected in Bangladesh represented by Bang373 and the Indian virus CAL-1 were considered as virtually identical viruses which are genetically distinct from ADRV, and it was suggested that Bang373 (CAL-l)-like group B rotavirus (Bengali strains) might have been primarily distributed to an are around the Bay of Bengal.