Noroviruses, Sapoviruses, and Astroviruses

Noroviruses: Evolutionary Dynamics, Epidemiology, Pathogenesis, and Vaccine Advances—A Comprehensive Review

“…(2) whether the magnitude or duration of protective immune response elicited by the nonreplicating antigens will be long enough to be clinically relevant and finally; (3) whether the vaccine will protect more vulnerable groups such as children and the elderly or whether the same formulations will be effective for different populations (high-income versus low income) [12,109,115].…”

“…The generation of point mutations in the norovirus RNA genome has been widely observed during long-term norovirus infection in both immunocompetent hosts [ 27 , 28 , 29 , 30 ] and immunocompromised individuals [ 12 , 31 , 32 , 33 ]. Like the other RNA viruses, the lack of proofreading repair mechanisms associated with the RNA replicates and transcriptase activity remains the critical factor driving the accumulation of point mutations [ 34 ].…”

“…The commonest food vehicles for viral transmission are fresh or frozen soft fruits and vegetables, undercooked or raw seafood, and ready-to-eat foods, including salads and sandwiches, which, though they require handling, involve little or no further cooking [ 24 ]. In several norovirus outbreak investigations, foods such as leafy vegetables, raspberries, fruits, and shellfish which were irrigated with or grown in water that was contaminated with faeces and then eaten raw were implicated in the disease transmission [ 12 , 63 , 64 , 65 , 66 , 67 ]. Bivalve molluscs such as mussels, scallops, cockles, clams, and oysters accumulate multiple norovirus strains in their edible tissues via filter feeding [ 38 , 68 ], presenting opportunities for infectious human norovirus inter- and intragenotype co-infection and subsequent viral genomic recombination within the host [ 69 ].…”

“…Epidemiologically, seroprevalence studies have suggested that human exposures to norovirus occur frequently, with worldwide anti-norovirus antibody prevalence rates approaching >80% by adulthood. Nevertheless, adults repeatedly display a high degree of susceptibility to noroviruses when challenged naturally and experimentally [ 12 ]. In several early human challenge studies, some norovirus-infected volunteers were found to show susceptibility to reinfection by both the homotypic and heterologous strains [ 133 , 134 , 135 ].…”

“…Noroviruses are genetically diverse groups of emerging RNA viruses, which continue to evolve in humans through both point mutations and genome recombination [ 11 ]. Of note, variations in the amino acid sequences of viral proteins associated with genomic mutations have resulted in an increased period of virus-shedding [ 12 ], evasion of pre-existing immunity associated with past infections [ 13 ], and reduced virus clearance in patients infected with heterologous strains [ 14 ]. Currently, ten genogroups (GI–GX) comprising 60 distinct P-types and 49 capsid genotypes have been reported in association with human and animal infection worldwide [ 15 ].…”