Jpn. J. Infect. Dis., 63, 2010 Laboratory and Epidemiology Communications Epidemiology and Molecular Characterization of Sapovirus and Astrovirus in Japan, 20082009 Wisoot Chan­it, Aksara Thongprachum, Shoko Okitsu1, Masashi Mizuguchi, and Hiroshi Ushijima1* Department of Developmental Medical Sciences, Institute of International Health, Graduate School of Medicine, The University of Tokyo, Tokyo 113­0033; and 1Aino Health Science Center, Aino University, Tokyo 150­0002, Japan Communicated by Takaji Wakita (Accepted June 3, 2010) Sapovirus (SaV) and human astrovirus (HAstV) are known to cause acute gastroenteritis in infants and young children (1,2). As a member of the family Caliciviridae, SaVs have a single­stranded positive sense RNA genome and are divided into five genogroups (GIGV). At least 13 genotypes can be distinguished within GI and GII (3). HAstVs belonging to the family Astroviridae have been classified into eight serotypes HAstV­1HAstV­8. In general, HAstV­1 is the most prevalent whereas type 3, 4, 7, and 8 are rare (4,5). A total of 662 fecal specimens were collected from non­hospitalized children with acute gastroenteritis in pediatric clinics in six localities in Japan (Tokyo, Sapporo, Saga, Osaka, Shizuoka, and Maizuru) during July 2008June 2009. RNA was extracted and purified using the QIAamp Viral RNA Mini kit (Qiagen, Hilden, Germany). Multiplex RT­PCR with specific primers re­ sulted in the identification of SaV and HAstV (6). Nu­ cleotide sequences of SaV­ and HAstV­positive PCR products were determined using Big­Dye terminator cy­ cle sequencing kit and ABI Prism 310 Genetic Analyzer (Applied Biosystems, Foster City, Calif., USA). Phylo­ genetic trees were generated using the MEGA version 4 (7). The sequences of strains detected in the study had been submitted to GenBank under accession nos. HM030920HM030923 and HM106431HM106446 for SaVs and HM212532HM212542 for HAstVs. Out of 662 fecal specimens tested, SaV and HAstV Fig. 1. Phylogenetic analysis based on the partial capsid se­ were detected in 20 (3z)and11(1.7z) cases, respec­ quences of SaVs. The strains detected in the current study tively.MostofSaV(n 18, 90z)andHAstV(n 10, period are shown in bold type. The PEC strain is used as an 91z) infections occurred in infants and children º3 outgroup. years of age. SaV prevalence increased slightly during the cold months from December to February (n 12), while HAstV exhibited a peak in April (n 6), corre­ be classified into four lineages (1a1d), in which our sponding with spring. In a phylogenetic tree, the majori­ nine strains clustered into lineage 1d and the other strain ty of SaV sequences belonged to GI/1 genotype (n into lineage 1a (Fig. 2). 15, 75z), followed by GII/1 (n 4, 20z), and GI/3 According to the past 6 years of SaV surveillance, (n 1, 5z) (Fig. 1). HAstV­1 (n 10, 91z)wasthe SaV GI/1 was the most prevalent genotype during most prevalent followed by HAstV­3 (n 1, 9z). This 20032004, and thereafter genotype GI/6 dominated phylogenetic tree clearly showed that HAstVs­1 could over the GI/1 in 20042005 (6). Then, the GI/6 was re­ placed by GI/1 from 2005 until 2007 (8,9). GIV emerged as a predominant strain in 20072008 (10). Surprisingly, *Corresponding author: Mailing address: Aino Health GI/1 emerged and became the prevailing genotype in Science Center, Aino University, 2­17­3 Shibuya, Shibuya­ the present study, while GIV suddenly disappeared. ku, Tokyo 150­0002, Japan. Tel & Fax: {81­3­3486­8481, This sudden disappearance of GIV might indicate that E­mail: ushijima­hiroshijcom.home.ne.jp the virus appeared at the time that the pediatric popula­ 302 should be continued in order to identify the trend of these viruses in the coming year. Acknowledgments This study was supported by Grants­in­Aid from the Ministry of Education, Culture, Sports, Science and Tech­ nology and the Ministry of Health, Labour and Welfare, Japan. The authors gratefully acknowledge the cooperation extended by Drs Shuichi Nishimura, Hideaki Kikuta, Tsuneyoshi Baba, Atsuko Yamamoto, Kumiko Sugita, Masaaki Kobayashi, Shintaro Hashira, and Takeshi Tajima for fecal specimen collection. Conflict of interest None to declare. REFERENCES 1. Nguyen, T.A., Hoang, L., Pham Le, D., et al. (2008): Identifica­ tion of human astrovirus infections among children with acute gastroenteritis in the southern part of Vietnam during 20052006. J. Med. Virol., 80, 298305. 2. Pang, X.L., Lee, B.E., Tyrrell, G.J., et al. (2009): Epidemiology and genotype analysis of sapovirus associated with gastroenteritis outbreaks in Alberta, Canada: 20042007. J. Infect. Dis., 199, 547551. 3. Akihara, S., Phan, T.G., Nguyen, T.A., et al. 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