Epidemiological characteristics of asymptomatic Norovirus infection in a population from oyster (Ostrea rivularis Gould) farms in southern China

Abstract

The following paper investigates the prevalence and characteristics of asymptomatic norovirus infection in the population living around oyster farm sites. Two consecutive surveys were conducted from January 2014 to December 2014 and 4549 stool samples were screened during the same time period. The total asymptomatic infection rate was 4.04% (184/4549). Norovirus infection rate was 5.20% in oyster farming population which was significantly higher compared with non-farming population where the infection rate was 3.65% (χ2 = 5.49, P < 0.05). A total of 184 NoV positive samples were identified by real time-quantitative polymerase chain reaction (RT-qPCR) and semi-nested RT-PCR and 136 sequences were obtained. The sequences were clustered into 14 genotypes. GI strains were clustered into six genotypes, including GI.2, GI.3, GI.5, GI.6, GI.8 and GI.9; while GII strains were clustered into GII.2, GII.3, GII.4, GII.5, GII.6, GII.8 and GII.13. GI.9 and GII.17 were the predominant and most prevalent genotypes, respectively. The GII.17 genotype replaced GII.4 becoming the dominant genotype in the oyster farming area in 2014. To sum up, long-term monitoring of asymptomatic infection is crucial for the detection of new variant strains and for identifying outbreaks during the early stage.

Detection and Genetic Correlation Analysis of Diarrhea Cases and Norovirus in Oysters in Yantai, China

“…The total infection rate of asymptomatic infected persons was 4.04%, and the incidence rate of NoV-infected cultured oyster population was 5.20%. The genotypes were diverse, GI.2, GI.3, GI.5, GI.6, GI.8, GII.3, GII.4, GII.5, GII.6, GII.8, GII.13, and GII.17 ( 17 ).…”

Spread of genetically similar noroviruses in Bangkok, Thailand, through symptomatic and asymptomatic individuals

“…The study identified GII.4 as the most common genotype in asymptomatic individuals. The predominance of GII.4 in asymptomatic individuals has been reported in Tanzanian and American Indian children ( Grant et al., 2017 ; Moyo et al., 2014 ), while the dominance of non-GII.4 genotypes in asymptomatic individuals has also been reported in other countries ( Wang et al., 2018 ; Bucardo et al., 2017 ; Utsumi et al., 2017 ; Koo et al., 2016 ). These findings suggest that genotype distributions in symptomatic and asymptomatic individuals vary depending on the setting or country.…”

Characterization of Antigenic Relatedness Among GI Norovirus Genotypes Using Serum Samples From Norovirus-Infected Patients and Mouse Sera

“…Compared to GI.3, GI.9 gained a high affinity to non-secretors, but lower affinities to A and AB, which could be explained by the two mutations at the binding interface and the surrounding area. To our knowledge, the binding feature of GI.9 is firstly characterized and it shows broad-spectrum affinity to all HBGA phenotypes, which partly explain GI.9 as the highest asymptomatic NoV infection in Changsha Bay farm sites ( Wang et al, 2018 ).…”

“…The P domain encoding sequences were cloned into T-vectors (Thermo Fisher, United States). The resulting variant fragments were GI.3 (the outbreak strain), GI.9 (extracted from stool sample provided by Guangdong CDC) ( Wang et al, 2018 ) and GI.2 (accession number KF306212 ).…”

“…The distribution of GI variants as the most predominant strain was reported in sub-Saharan Africa with GI.7 (33%), GI.3 (21%), and GI.5 (17%) from 1993 to 2015 ( Munjita, 2015 ). Moreover, a study investigating the prevalence and characteristics of asymptomatic NoV infection suggested GI.9, GI.2, and GI.3 accounted for 39.7% asymptomatic infection among people living around oyster farms in south China ( Wang et al, 2018 ). A surveillance analysis of AGE cluster in Taiwan revealed 16.5% NoV positive for GI of which GI.3 was the most predominant genotypes accounting for 36.8% thus suggested a close monitor of GI.3 prevalence ( Chiu et al, 2020 ).…”