Molecular Epidemiology Study Of Norovirus-Associated Diarrhea In Children In Chongqing,2014

Objective:To study the prevalent situation and clinical characteristics of norovirus associated acute viral diarrhea in children, and analyze the genotypes and recombination in Chongqing,2014.Methods:Five hundred and eleven diarrhea samples were collected from children with acute viral diarrhea at the clinical laboratory center of the Children’s Hospital of Chongqing Medical University and the clinic data were recorded in 2014. RT-PCR method was used to detect the nucleic acid about capsid region of NV GI and GII. All the positive products were sequenced, and then use software analyze the genotypes and established the phylogenetic tree. To study the NV recombination,the both RdRp and Capsid regions of all the positive products were amplified, and then analyzed the RdRp and Capsid genotypes by software, at last use SimPlot software to identify the recombination.Results:Five hundred and eleven specimens were collected (290 males and 221 females), but no one was positive for genogroup GI and 67 (13.1%) positive for genogroup GII, the positive rate in the male was 13.1%(38/290), the females positive rate was 13.1%(29/221), And there was no significant difference of NV detection rate between male and female(x2=0.000, P>0.05). NV were detected through out the other months except for April, and the NV detection rate was significantly difference between different month(x2=58.583,P<0.05). The positive rate at the age group between seven to twelve month was higher than other groups, and children under 2 years old of the total positive cases accounted for 86.6%. The NV positive children with vomiting, respiratory symptoms and fever were 53.7%(36/67),28.4%(19/67) and 10.5%(7/67), respectively. Five genotypes based on capsid gene diversity were identified in 67 norovirus strains,includingGII.4Sydney2012(42/67,62.7%),GII.3(8/67,11.9%),GII.17 (8/67,11.9%),GII.6(7/67,10.5%), GII. 14(2/67,3.0%).59 norovirus strains were sequenced successfully in the both RdRp and Capsid regions at the same time,52 specimens were recombination strains and 4 recombination types of NV GⅡ were detected, including GII.e/GII.4Sydney2012(42/59,71.2%), GⅡ.12/GII.3(6/59,10.1%), GII.7/GII.6(2/59,3.4%), GII.7/GII.14(2/59,3.4%).Conclusions:NV is a common pathogen of pediatric viral diarrhea in Chongqing, and there was no significant difference of NV detection rate between male and female. The NV epidemic peak is August, September and October, the peak age group is 7 to 12 month and children under 2 years old of the total positive cases accounted for 86.6%, vomiting is the main accompanying symptoms of NV enteritis. The epidemic strains of NV in Chongqing include five genotypes, GII.4 Sydney2012 is the predominant strain, followed by GII.3, GII.17, GII.6 and GII.14. NV recombination was very common,4 recombination types of NV GII were detected, including GII.e/GII.4Sydney2012, GII. 12/GII.3, GII.7/GII.6 and GII.7/GII.14.