Detection and genetic characterization of rotavirus infections in non-hospitalized children with acute gastroenteritis in Japan, 2007–2009

Abstract

The molecular epidemiology of rotavirus infections in non-hospitalized children in five different regions (Sapporo, Saga, Tokyo, Osaka, and Maizuru) of Japan during 2007–2009 was investigated. Overall, rotavirus was detected in 156 out of 1008 (15.5%) specimens. The rotavirus infection in 2007–2008 (19.3%) was higher than those in 2008–2009 (12.1%). G1P[8] was the most prevalent (62.8%), followed by G3P[8] (21.8%), G9P[8] (14.7%), and G2P[4] (0.7%). Interestingly, the number of G3P[8] strains increased threefold from the former season (2006–2007) from 7.3% to 21.8%, whereas G2P[4] and G9P[8] decreased from 11.4% to 0.7% and 20.3% to 14.7%, respectively. In the phylogenetic analysis, G3 rotaviruses were closely related to “the new variant G3” 5091 strain, which previously emerged in Japan and China. G9 viruses isolated in 2007–2008 were genetically close to the Thai strain, while those isolated in 2008–2009 had a close relationship with Chinese strains. G1 viruses appeared to be more similar to the recently reported G1 strain in China. Nucleotide sequence analysis of 33 P[8]-nontypeable strains revealed 5 nucleotide mismatches at the primer binding site. Based on previously reported (2003–2007) and current (2007–2009) data of rotavirus surveillance in the five areas of Japan, it was revealed that in Sapporo, Osaka, and Maizuru, G1P[8] and G3P[8] were detected at high frequencies, ranging from 47.2 to 57.7% and 31.7 to 47.4%, respectively. In Tokyo, G1P[8] (47.4%) was the predominant strain, followed by G9P[8] (20.6%), whereas in Saga, G3P[8] (38.9%) and G9P[8] (36.1%) were identified as the most dominant types. None of G9P[8] was detected in Sapporo. This study highlights the genetic diversity and the significance of rotavirus diarrhea in Japan.