We investigated the genotypic changes and epidemiologic features of norovirus outbreaks, as well as factors influencing the attack rate and outbreak duration in Wuxi from 2014 to 2018. Norovirus outbreaks, monitored through surveillance system, were investigated. The norovirus-positive specimens from outbreaks were collected and genotyped using a dual polymerse-capsid genotyping protocol based on a one-step PCR amplicon. The genotypes were analyzed by Norovirus Typing Tool Version 2.0. A total of 74 norovirus outbreaks were reported in Wuxi from 2014 to 2018.Most(93.2%) norovirus outbreaks were caused by GII genotypes. The predominant norovirus genotypes in outbreaks have changed from GII.17 (20.3%) in 2014-2015 to GII.P16/GII.2 (40.5%) in 2017-2018. GII.P16/GII.2 in 2017-2018 season were more prevalent than GII.17 in 2014-2015 season (χ² =4.741, P=0.029). 56.7% of outbreaks occurred in primary school. The reinfection rate of norovirus outbreaks was 16.2%. 66.7% of reinfection outbreaks were infected by variants different to previous infections. Outbreaks occurred in non-primary school settings(P=0.02) and that with setting suspension (P=0.025) experienced a higher attack rate. The outbreaks in primary schools(P=0.024), reinfection outbreaks (P=0.035) and longer report timing  (P=0.001) declared a significantly longer duration. It is of great importance that the monitoring of norovirus outbreaks for the emergence of novel strains, along with responsive preventive and control interventions, should be strengthened in adults and school-age population, especially in primary students and preschool children.

Norovirus outbreaks; Genotypes; Reinfection; Epidemiologic feature; Influencing factors.