Norovirus is highly infectious and can be transmitted through contaminated water or food.Norovirus is one of the important pathogens causing the outbreak of acute non-bacterial gastroenteritis.In recent years,norovirus gastroenteritis has become an outbreak and epidemic in the world,which is an important public health problem in the world.In recent years,there have been outbreaks in many provinces and regions in China.Norovirus epidemic also exists in Xiamen,which is one of the main pathogens of viral diarrhea in this area.Oysters tend to accumulate a large number of pathogenic factors,such as norovirus,in the digestive tract and other visceral mass when they are filtered.There are a lot of reports at home and abroad that oysters are contaminated by Norovirus,which causes outbreaks of gastroenteritis.However,there are few studies on the contamination status of Norovirus in oysters sold in Xiamen.In view of the prevalence of norovirus in Xiamen,and the high incidence of norovirus aggregation gastroenteritis in Siming District,and the vulnerability of the virus to mutation into new subtypes,and the high risk of infection of the new subtypes to the population,we carried out the monitoring of norovirus in oysters in Xiamen area,and sequenced the positive samples of norovirus in oysters and gastroenteritis cases.Then the following results are obtained:(1)From 2015 to 2016,the norovirus contamination rate of oysters sold in xiamen was relatively high,with a detection rate of 14.19%.The detection rate of GⅠ group was 3.66%,GⅡ group was 7.74%(36/465),and the detection rate of GⅠ group and GⅡ group was 2.58%.The detection rate in GⅠ group was higher in Bingzhou than in Hecuo and Bashi,and Hecuo and Bashi were both higher than in Zhongpu.The detection rate of GⅠ+GⅡ in 2016 was higher than that in 2015.The detection rate of G Ⅰ+GⅡ was higher in winter and spring than in summer and autumn.There were no statistically significant differences in the detection of norovirus and gene groups in oysters from xiamen and zhangzhou.Quantitative analysis showed that the oyster pollution level in xiamen was relatively high.The maximum logarithmic value of the loads of norovirus in oyster digestive gland was 5.30 and the logarithmic mean was 3.47.The highest loads of GⅠ group was 3.52,and the logarithmic mean was 3.24.The highest loads of GⅡ group was 5.30,and the logarithmic mean value was 3.24.(2)The detection and analysis of norovirus gastroenteritis in Siming district showed that there were 20 cases of norovirus aggregation gastroenteritis in 2015-2016,of which 65.00%were GⅡ group according to the year.There was no single infection in GⅠ group,indicating that gastroenteritis mainly occurred in GⅡ group.According to the year analysis,the composition ratio of GⅡ events in 2015 was higher than that in 2016,and the incidence of GⅠ+GⅡ mixed infection in 2016 was higher than that in 2015.According to seasonal analysis,GⅡ events and GⅠ、GⅡ mixed infection events occurred mainly in winter,and there was no difference in genome composition ratio of gastroenteritis events in spring,autumn and winter.(3)Norovirus positive samples were sequenced and analyzed,and the norovirus sequencing genotypes in oyster samples were classified into five genotypes:GⅡ.3,GⅡ.13,GⅡ.17,GⅡ.2,GⅡ.Among them,4 strains of GⅡ.17 type were the main successful sequencing genotypes.GⅠ.6,GⅠ.2,GⅠ.3,GⅡ.17,GⅡ.13,GⅡ.4_Sydney 2012,GⅡ.3,GⅡ.Gastroenteritis events were dominated by single genotype infection,and GⅡ.17 was the main infection type,which was the main epidemic dominant type in Siming distict.Mixed multi-genotype infection events accounted for a certain proportion,which should be paid enough attention to the disease prevention and control department.In 2015,single-genotype infection was dominant,and there was no polygenotype mixed infection.In 2016,poly genotype mixed infection was the main type,and GⅡ.17 infection was the main type in the two years.In 2015,single genotype infection was the main type and no multiple genotype mixed infection was found.Compared with 2015,GⅠinfection,including GⅠ.2,GⅠ.3,GⅠ.6,and GⅠ.6,were found in 2016 and 2 cases were GⅠ.6.The results showed that in 2016,although the infection genotype was mainly GⅡ.17,the genotype was more diversified,and new genotype infection events occurred,which should be paid attention to the prevention and control department.Norovirus gastroenteritis occurred mainly in winter,but not occurred in summer.The winter gastroenteritis events were mainly single GⅡ.17 type and mixed infection containing GⅡ.17 type.Mixed polygenic infections occurred in winter and spring,while single genotype infections occurred in autumn.These should cause the prevention and control department’s enough attention.(4)Homology analysis and phylogenetic tree analysis of GⅠ and GⅡ strains showed that VP1 sequences of multiple norovirus gastroenteritis events in Siming district were highly homologous,possibly caused by the same virus strain.For example,the gastroenteritis event(event 12)of strain 160215JC05 was highly homologous with the gastroenteritis event(event 13)of strain 160218JC03,which may be caused by the infection of the same G 1.2 strain.The 150127JC02 strain was highly homogenous to the gastroenteritis event(event 5),150222JC02(event 6),150223JC02(event 7),160215JC01(event 12),160218JC01(event 13),160219JC01(event 14),160412JC03(event 16),and 16S66(event 19),which may be caused by the same GⅡ.17 strain.Moreover,multiple oyster norovirus strains with multiple genotypes were highly homologous with gastroenteritis event strains,for example,oyster GⅠ.2 strain BS160330053 was highly homologous with 160215JC05 and 160218JC03 strains.Oyster strain BS15101302 and oyster strain BS16033005 are highly homologous with gastroenteritis strain 150127JC02,gastroenteritis strain 150222JC02,gastroenteritis strain 160215JC01,gastroenteritis strain 160218JC01 and gastroenteritis strain 160219JC01.This suggests that the oyster norovirus strain may be associated with the corresponding gastroenteritis event-strain.In this study,the successful sequencing strains of GⅠ type and GⅡ type were compared with the reference strains of GenBank,and it was found that many successful sequencing strains were highly homologous with the corresponding strains of GenBank. |