Objective: To analyze the epidemiological characteristics of norovirus-caused acute gastroenteritis outbreaks in China, identify the factors influencing the scale of outbreaks, and provide scientific evidences for early control of norovirus infection outbreaks. Methods: The descriptive epidemiological analysis approach was applied to analyze the incidence of national norovirus infection outbreaks by using the data from the Public Health Emergency Event Surveillance System in China from January 1, 2007 to December 31, 2021. The unconditional logistic regression model was applied to analyze the risk factors that affected the outbreaks' scale. Results: A total of 1 725 norovirus infection outbreaks were recorded in China from 2007 to 2021, with an upward trend in the number of the reported outbreaks. The southern provinces had their annual outbreak peaks from October to March; the northern provinces had two outbreak peaks from October to December and from March to June annually. The outbreaks occurred mainly in southeastern coastal provinces with a trend of gradual spread to central, northeastern and western provinces. The outbreaks mainly occurred in schools and childcare setting (1 539 cases, 89.22%), followed by enterprises and institutions (67 cases, 3.88%) and community households (55 cases, 3.19%). Human to human transmission was the main infection route (73.16%), and norovirus GⅡ genotype was the predominate pathogen causing the outbreaks (899 cases, 81.58%). The time interval between the onset of the primary case and the outbreak reporting M (Q1, Q3) was 3 (2, 6) days and the case number of the outbreak M (Q1, Q3) was 38 (28, 62). The timeliness of outbreak reporting was improved in recent years and the scale of the outbreaks showed a decreasing trend over the years, the differences in reporting timeliness and outbreak scale among different settings were significant (P<0.001). The factors that affected outbreaks' scale included the outbreak setting, transmission route, outbreak reporting timeliness and type of living areas (P<0.05). Conclusions: From 2007 to 2021, the number of the norovirus-caused acute gastroenteritis outbreaks increased in China and the more areas were affected. However, the outbreak scale showed a decreasing trend and the outbreak reporting timeliness was improved. It is important to further improve the surveillance sensitivity and reporting timeliness for the effective control of the outbreak scale.
目的： 分析我国诺如病毒急性胃肠炎暴发疫情流行病学特征，探讨暴发疫情规模的影响因素，为及早控制暴发疫情提供科学依据。 方法： 对突发公共卫生事件管理信息系统2007年1月1日至2021年12月31日全国诺如病毒急性胃肠炎暴发疫情进行描述性流行病学分析，应用非条件logistic回归模型分析暴发疫情规模的影响因素。 结果： 2007-2021年共报告暴发诺如病毒急性胃肠炎疫情1 725起，报告疫情起数呈上升趋势。南方省份每年10月至次年3月为疫情高峰，北方省份疫情高峰为每年10-12月和次年3-6月。疫情报告地区从东南沿海省份逐步向中部、东北和西部省份扩散。疫情主要发生在学校和托幼机构（1 539起，89.22%），其次为企事业单位（67起，3.88%）和社区家庭（55起，3.19%）。人与人接触为主要传播途径1 262起（73.16%），GⅡ基因型为引起暴发疫情的主要病原型别（899起，81.58%）。首例病例发病至疫情报告时间间隔M（Q1，Q3）为3（2，6）d，疫情规模M（Q1，Q3）为38（28，62）例。近年来，疫情报告及时性提升，疫情规模随年份呈下降趋势，二者在不同发生场所之间差异均有统计学意义（P<0.001）。发生场所、传播途径、报告及时性和居住地类型是暴发疫情规模的影响因素（P<0.05）。 结论： 2007-2021年我国诺如病毒急性胃肠炎暴发疫情整体呈上升趋势，疫情波及地区范围不断扩大，但疫情发生规模整体呈下降趋势，疫情报告及时性提升，提高监测灵敏度和及早报告可有效控制疫情发生规模。.