Distribution of Human Sapovirus Strain Genotypes over the Last Four Decades in Japan: a Global Perspective

Sapovirus (SaV) infections are a public health problem because they cause acute gastroenteritis in humans of all ages, both sporadically and as outbreaks. However, only a limited amount of SaV sequence information, especially whole-genome sequences for all the SaV genotypes, is publicly available. Therefore, in this study, we determined the full/near-full-length genomic sequences of 138 SaVs from the 2001 to 2015 seasons in 13 prefectures across Japan. The genogroup GI was predominant (67%, n = 92), followed by genogroups GII (18%, n = 25), GIV (9%, n = 12), and GV (6%, n = 9). Within the GI genogroup, four different genotypes were identified: GI.1 (n = 44), GI.2 (n = 40), GI.3 (n = 7), and GI.5 (n = 1). We then compared these Japanese SaV sequences with 3,119 publicly available human SaV sequences collected from 49 countries over the last 46 years. The results indicated that GI.1, and GI.2 have been the predominant genotypes in Japan, as well as in other countries, over at least four decades. The 138 newly determined Japanese SaV sequences together with the currently available SaV sequences, could facilitate a better understanding of the evolutionary patterns of SaV genotypes.