Epidemiology of Norovirus among outpatients presenting with acute diarrhea in Dalian, China

The aim of this study was to perform an epidemiological analysis of the viral strains isolated from outpatients with acute gastroenteritis in Dalian, Liaoning province, China to determine the epidemiology of Norovirus (NoV). Fecal samples were collected from 789 outpatients with acute gastroenteritis in the Xigang district of Dalian, Liaoning province, China from July 2015 to December 2016. Norovirus was detected by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). A selection of the positive samples identified was subsequently sequenced, and these data were analyzed by using the Norovirus Typing tool. Results showed that 38.02% (300/789) of the fecal samples were positive for NoV, of which 95.67% (287/300) were identified as genotype GII with 1.33% (4/300) identified as GI. A further 3.00% (9/300) were combined infections with both GI and GII Norovirus. When analyzing the age distribution, the infections primarily occurred in adults especially the elderly whose NoV positive rate was much higher than the average. Winter was the season when most cases were recorded during 2015 and 2016; however, another infection peak was observed in July 2016. Thirty Norovirus positive samples were successfully sequenced, and results showed that GII.4 was the most commonly identified genotype, along with GII.3 and GII.17. Norovirus is the most common pathogen for acute gastroenteritis in Dalian, Liaoning province of China. The current NoV genotype prevalence in Dalian was found to be similar to that in other regions of China. Genotype GII.4 was the most common genotype in our study, GII.3 and GII.17 were also identified.