A Study On Molecular Epidemiology Of Noroviruses Among Jiangmen's Children And Adults

Objective:1. To investigate the epidemiology characteristic and predominant strain of Noroviruses (NV) among the children with non-bacterial diarrhea in Jiangrnen betweenSep. 2005 and Jan. 2007.2. To study the pathogenic relation between NV and the acute non-bacterialdiarrhea in adult, and determine the genotypes of the NV during NV epidemic phase.3. To search for the clinical characteristic and main risk factors for NVinfections in adult and childrens.Methods:1. 15 days every month., fecal speciments were collected from non-bacterial dirrheachildren in Jiangmen Maternity & Child Health Care Hospital between Sep. 2005 and Jan.2007. Test conclusions were reported to the patients and questionnaires werecompleted by communicating with telephone. And, fecal speciments of acute non-bacterialdiarrhea in adult were collected from Jiangrnen People's Hospital every day inepidemic phase.2. Rotavirus were detected with Rotavirus Group A Diagnostic Kit (Colloidal Gold Device), and rotavirus-negative specimens were detected for NV byreverse-transcription polymerase chain reaction(RT-PCR). Some amplicons obtainedfrom NV-positive stools were purified and sequenced. Phylogenetic tree was createdfor strain characterization and determine the predominant genotype of the NV.3. To assess the medical importance of NV infection, the clinical characteristicsof children infected with NV were compared with those found in patients infectedwith rotavirus. And a 1:1 case-control study was performed with the objective ofidentifying the risk factors for sporadic NV infection. The potential risk factorsiNVestigated were the consumption of different foodstuffs, contact withgastroenteritis persons and personal hygiene. Returned questionnaires were coded anddouble-entered into EpiData 2.1a. Qualitative data statistical analysis was performedwith chi-square test, and quantitative data was carried out with 2 sample t-test forindependent samples or nonparametdc test by SPSS12.0. All tests were two-tailedand considered significant when the P-value was＜0.05. A 1:1 conditional logisticregression model was used to study the independent effects of risk factors with anassociation in the univariate analyses with a P-value＜0.15. Selection of variables inthe model was stepwise manually, based on the log-likelihood ratio.Results:362 fecal specimens were collected from non-bacterial diarrhea children inJiangrnen, and NV positive rate was 14.36％(32/362) in 2006. During NV epidemicphase, 9.03％(27/299) and 20.35％(146/266) were positive for NV of patients withnon-bacterial diarrhea in 2006 and 2007, respectively. And there was statisticalsignificance. NV detection was mainly distributed in children under 2 years old, butwas similarity in every month of the season. All 35 sequenced strains belonged to NVin which 32 strains were GⅡ-4, 2 strains were GⅡ-3, 1 strain was recombination geneand could not identify the genetype. 17.86％(10/56) NV was detected in adults with acute non-bacterial diarrhea during NV epidemic phase. All 10 sequenced strainsbelonged to NV in which 9 strains were GⅡ-4, 1 strains were GⅡ-3. From the 81cases positive for NV, 49 (60.5％) were associated with vomiting, 16 (19.8％) fever,19 (23.5％) dehydration, 9 (11.1％) abdominal pains and 8 (9.9％) cough. The firstsymptom were vomiting and diarrhea,and the proportion were 41.9％(34/81) and44.4％(36/81) respectively. Our findings showed that the mean NV clinical severitywas equal to that in rotavirus gastroenteritis except that vomiting proportion of NVwas more than RV and fever proportion was less than it. Consumption of crude orcold foods is a doubtful risk factor for NV infection, contact with gastroenteritispersons is the risk factor and washing hands before dinner is the protective factor.Conclusions:1. NV are important etiological agent of viral gastroenteritis in people of all agegroups. Every month had NV detected among the children with non-bacterial diarrheain 2006. And NV epidemic phase is from Sep.to Jan. of the next year. Positive rate ofNV among children with non-bacterial diarrhea during NV epidemic phase in 2006was higher than which in 2005. And it was identical to the reports that NV wereepidemic in Southeast Asia.2. There were different genotypes circulated among children, and no other NVgenetic cluster was detecded except for GⅡ-4 in adult in Jiangmen city.NV GⅡ-4genetic cluster was the predominant strain.3. Diarrhea and vomiting were predomaine of the earliest symptomes in childrenNV diarrhea. Which proportion was 44.4％(36/81) and 41.9％(34/81). And thesymptoms in adult NV diarrhea were less than children's.4. Uncook and cold food were one of the risk factors of NV infection. And keepgood personal hygiene will prevent the occurrence and spread of NV infection.