Introduction: Human noroviruses are the leading cause of acute viral gastroenteritis (AGE) worldwide in all age groups. GII.4 strains have been the predominant genotype circulating globally over the last 2 decades and since 2012. GII.4 Sydney viruses have emerged and caused the majority of AGE outbreaks worldwide.Methods: Data from norovirus outbreaks from the laboratory-based surveillance of norovirus outbreaks in China (CaliciNet China) between October 2016-December 2020 were analyzed.Results: During October 2016-December 2020, 1,954 norovirus outbreaks were reported, and positive fecal samples from 1,352 (69.19%) outbreaks were genotyped. GII.4 Sydney [P31] viruses accounted for 2.