Human sapoviruses: genetic diversity, recombination, and classification

The family Caliciviridae contains four genera Sapovirus, Norovirus, Lagovirus and Vesivirus, which include Sapporo virus (SaV), Norwalk virus (NoV), Rabbit hemorrhagic disease virus (RHDV) and Feline calicivirus (FCV), respectively. SaV is a causative agent of gastroenteritis in children and adults. SaV can be divided into five genogroups (GI-GV), among which GI, GII, GIV and GV are known to infect humans, whereas SaV GIII infects porcine species. Detection methods include ELISA, RT-PCR and real-time RT-PCR. Since few SaV studies have been conducted, it is difficult to draw correlations between or conclusions about rates of incidence, detection and overall prevalence. Nevertheless, most studies agree that SaV infection is more frequent in young children than adults and that infection in children almost always occurs by 5 years of age. In addition, children at day-care centres and institutions are at greatest risk of SaV-associated infection and transmission. Recently, a number of important findings concerning human SaV were discovered. SaV strains were detected in water samples, which included untreated wastewater specimens, treated wastewater samples and river samples. SaV strains were also detected in shellfish samples destined for human consumption, and recombinant SaV strains were identified in a number of different countries. The purpose of this review was to highlight the current knowledge of human SaV, which appears to be an increasingly important virus causing gastroenteritis in humans.