| Objective:1 To study the epidemiology characteristic of Norovirus (NV) infection among infants and children with viral gastroenteritis in Tianjin area.2 To study the predominant prevalence strain of NV in Tianjin area.3 To search for the main clinical characteristic of NV infection in infants and children.4 To compare the NV detected ratio of primer P289/290 and JV12Y/JV13I.Method:Fecal specimens were collected from cases of viral gastroenteritis in Tianjin Children Hospital from August 2008 to July 2009. Rotavirus were detected with Rotavirus Group A Diagonostic Kit and rotavius-negative specimens were detected for NV by reverse-transcription polymerase chain reaction (RT-PCR).then some of the positive samples were sequenced and compared with the NV. sequences deposited in Genbank. The nucleotide sequence homology was evaluated with BioEdit software and the phylogenetic tree was generated by DNAstar software. The clinical data also were collected, Qualitative data statistical analysis was performed with chi-square test, and quantitative data was carried out with 2 sample t-test for independent samples or nonparametric test by SPSS 11.5.Results:1,540 fecal specimens were collected from viral gastroenteritis in Tianjin area,and the NV. positive rate was 32.22% between August 2008 and July 2009.2,All sequenced strains belonged to NV Gâ…¡-4,which were almost identical to the variants causing epidemics in the world. The sequence TJC0801 has high identities to the strain Beijing208 obtained from Beijing,2006. Strain TJC0802, TJC0806 has high identities to the Nijmegen115/2006/NL. And the sequence TJC0803 is more closer to the sequence Seoul 0534, obtained from Korea,2007. Sequence TJC0804 is closer to the sequence Seou10552/2007/KR, Seou10534/2007/KR. TJC0805 TJC0901 and TJC0902 has high identities to Kumamoto5 obtained from Japan 2006. TJC0807 has high identities to Seou10552/2007/KR, Seoul 0545/2007/KR and Shenzhenl73-06.TJC0808 has high identities to Beijing361/2007/CHN, Beijing310/2007/CHN. TJC0809 is closer to Akital/2006/JP. The sequence of TJC0903 and TJC0905 are closer to Beijing133/2007/CHN. The sequence TJC0906 is closer to the sequence of Beijing96/2007/CHN, Beijing 10/2007/CHN. Besides the sequence TJC0904,14 of all sequences belonged to Gâ…¡-4/2006b. And the sequence TJC0904 is a recombinant strain of NV, which is closer to the sequence Seoul 0229 obtained from Korea,2008.3,From 174 cases positive for NV,26 (14.94%) were associated with vomiting, 9(5.17%) fever. Egg-pattern stool were found 84(48.28%), paste-like stool were 51(29.31%), dilute-water stool were 39(22.41%). The highest positive rate (62.22%) was found in November, and the lowest positive rate was found in August. Our finding showed that infants and children 12-17 months old has higher positive rate of NV,which were 29.93%, then followed by children who were 3-5 months old,which positive rate was 18.97%.87.36% NV positive cases distributed among children under 2 years old. The difference of the positive rate between male and femal is not significant.4,NV detected ratio of primer P289/290 is 21.33%, while the primer JV12Y/JV13I is 17.41%. The differences of two primer's detected radio is significant (p<0.05).Conlusion:Norovirus(NV) was important causing viral gastroenteritis in infants and children in Tianjin area from August 2008 to July 2009. NV Gâ…¡-4 genetic cluster was the predominant strain and no other genetic cluster was detected, NV detection was mainly distributed among children under 2 years old, and the highest positive rate was fond in Noverber. The primer P289/290 has a higher detected radio than the primer JV12Y/JV13I.
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