Molecular epidemiology of norovirus infection among sporadic cases of acute gastroenteritis in Nanning city

Objective To characterize molecular epidemiological features of norovirus infection among sporadic cases with acute gastroenteritis in Nanning city.Methods The epidemiological data of diarrheic patients from outpatient clinics of a hospital in Nanning city between January 2007 and December 2008 were analyzed.A total of 696 fecal specimens were collected from the patients and screened for the presence of norovirus RNA using real-time reverse transcription-polymerase chain reaction.Some positive specimens were selected randomly and subjected to sequencing and phylogenetic analysis to identify their genotypes.Results Of 696 specimens,183(26.30%) were positive for norovirus RNA; among them,180(98.36%) belong to genogroup Ⅱ(GⅡ) and the remaining 3(1.64%) belong to genogroup I(GI).Of the 30 GⅡ strains randomly selected for sequencing analysis,the predominant genotype was GⅡ4(26 cases),followed by GⅡ12(2 cases),GⅡ7(1 case),and GⅡ16(1 case).The 3 GI strains were classified into three genotypes:GI2,GI4,and GI8.The sporadic norovirus infection occurred preferentially during the cold season.There were no statistical differences in the detection rate among the patients of different genders and age groups.Conclusion The findings suggest that noroviruses are a major etiologic agent of sporadic gastroenteritis in Nanning city.The GⅡ4 is the predominant genotype,co-circulating with other diverse genotypes.