Objective: To assess the imported risk of COVID-19 in Guangdong province and its cities, and conduct early warning. Methods: Data of reported COVID-19 cases and Baidu Migration Index of 21 cities in Guangdong province and other provinces of China as of February 25, 2020 were collected. The imported risk index of each city in Guangdong province were calculated, and then correlation analysis was performed between reported cases and the imported risk index to identify lag time. Finally, we classified the early warming levels of epidemic by imported risk index. Results: A total of 1 347 confirmed cases were reported in Guangdong province, and 90.0% of the cases were clustered in the Pearl River Delta region. The average daily imported risk index of Guangdong was 44.03. Among the imported risk sources of each city, the highest risk of almost all cities came from Hubei province, except for Zhanjiang from Hainan province. In addition, the neighboring provinces of Guangdong province also had a greater impact. The correlation between the imported risk index with a lag of 4 days and the daily reported cases was the strongest (correlation coefficient: 0.73). The early warning base on cumulative 4-day risk of each city showed that Dongguan, Shenzhen, Zhongshan, Guangzhou, Foshan and Huizhou have high imported risks in the next 4 days, with imported risk indexes of 38.85, 21.59, 11.67, 11.25, 6.19 and 5.92, and the highest risk still comes from Hubei province. Conclusions: Cities with a large number of migrants in Guangdong province have a higher risk of import. Hubei province and neighboring provinces in Guangdong province are the main source of the imported risk. Each city must strengthen the health management of migrants in high-risk provinces and reduce the imported risk of Guangdong province.
目的： 评估广东省各市新型冠状病毒的疫情输入风险，并进行短期风险预警。 方法： 获取截至2020年2月25日广东省21个地级市和其他各省报告病例数及百度迁徙指数，计算广东省各城市的累计疫情输入风险指数，对输入风险指数与病例报告数进行相关性分析以确定滞后时间，最后根据风险指数划分疫情输入风险等级。 结果： 广东省累计报告确诊病例1 347例，90.0%的病例聚集在珠三角地区。广东省平均每天的疫情输入风险指数为44.03。在各市的输入风险来源中，湛江市的最大风险来自海南省，其他市均来自湖北省，广东省的相邻省份也有较大影响。广东省滞后4 d的疫情输入风险指数与每日新增病报告例数的相关性最高（r=0.73）。各市累计4 d的风险预警显示，未来4 d东莞、深圳、中山、广州、佛山和惠州市具有高输入风险，累计输入风险指数分别为38.85、21.59、11.67、11.25、6.19和5.92，最高风险仍来源于湖北省。 结论： 广东省外来人口较多的城市具有较高的疫情输入风险，湖北省和广东省的邻近省份是输入疫情的主要省份。.
Keywords: COVID-19; Early warning; Risk assessment.