Analysis of epidemiology characteristics of norovirus among diarrheal outpatients in 27 provinces in China, 2009-2013

Objective: to investigate the epidemiology characteristics of norovirus among diarrheal outpatients in China. Methods: diarrhea cases were monitored at emergency/outpatient departments at 173 hospitals in 27 provinces of China,with clinical and epidemiological data,and fecal specimens collected and sent to 58 network-laboratories to detect norovirus by RT-PCR method,and to analyze the positive rate of norovirus in various regions,population and time during 2009-2013. Results: 11.6? of the 34 031 diarrheal cases under surveillance were found with norovirus.Age group of 6-23 month-old children and that of people over 45 years old were found with the highest positive percentage,13.7? and 12.4? respectively.Positive percentage of norovirus peaks in autumn and winter in a year; it peaks in mid-temperate zones (10.7?) and warm-temperate zones (11.6?) in winter.It peaks in sub-tropical zones in autumn (14.3?).The most prevalent genogroups detected were norovirus G ?,accounting for 89.9? of identified strains. Conclusion: norovirus affects all ages and was most prevalent in children and the elderly among diarrhea outpatients.Norovirus' positive percentage showed strong seasonal pattern,and peaks at different times of a year in different climate zones of China.Since no effective preventive measures existed,further study on norovirus epidemiology and intervention strategies should be conducted in future