Department of Epidemiology, School of Public Health, Fudan University, Shanghai, China.
Key Laboratory of Public Health Safety of Ministry of Education, Fudan University, Shanghai, China.
PLoS Negl Trop Dis. 2020 Dec 7;14(12):e0008908. doi: 10.1371/journal.pntd.0008908. eCollection 2020 Dec.
As of October 5, 2020, China has reported 2,921 cases imported from overseas. Assessing the effectiveness of China's current policies on imported cases abroad is very important for China and other countries that are facing or will face overseas imported cases. In April, we used a susceptible-exposed-infectious-recovered metapopulation model to simulate the epidemic in seven foreign countries, China and the three Chinese key cities. Based on the model outside China, we estimated the proportion of people in incubation period and calculated the risk indexes for Chinese cities through analyzing aviation traffic data from these countries. Based on the model in China and the three key cities, we collected information on control measures and quantified the effectiveness of implementing the current policies at different times and intensities. Our model results showed that Shanghai, Beijing, Qingdao, Guangzhou, and Tianjin have the top five risk indexes. As of April 20, 2020, under current measures, the number of confirmed cases could be reduced by 99% compared with no air traffic restrictions and isolation measures; the reduction could be 93% with isolation of passengers only from key countries. If the current policy were postponed for 7, 10, or 20 days, the increase in the number of confirmed cases would be 1,329, 5,524, and 779,245 respectively, which is 2.1, 5.7, and 662.9 times the number of confirmed cases under current measures. Our research indicates that the importation control measures currently taken by China were implemented at an appropriate time to prevent the epidemic spreading and have achieved relatively good control results. However, it is necessary to remain vigilant; otherwise, another outbreak peak could occur.
截至 2020 年 10 月 5 日，中国已报告 2921 例输入性病例。评估中国目前针对境外输入病例的政策效果，对于中国和其他面临或即将面临境外输入病例的国家非常重要。今年 4 月，我们使用易感-暴露-感染-恢复的多人群模型模拟了 7 个国外、中国和中国 3 个关键城市的疫情。基于中国境外的模型，我们估计了潜伏期人群的比例，并通过分析这些国家的航空交通数据，计算了中国城市的风险指数。基于中国和 3 个关键城市的模型，我们收集了控制措施的信息，并量化了不同时间和强度实施当前政策的效果。我们的模型结果表明，上海、北京、青岛、广州和天津的风险指数位居前五。截至 2020 年 4 月 20 日，在当前措施下，与无航空限制和隔离措施相比，可减少 99%的确诊病例；仅对重点国家的旅客进行隔离，可减少 93%的确诊病例。如果当前政策推迟 7、10 或 20 天，确诊病例数将分别增加 1329、5524 和 779245 例，分别是当前措施下确诊病例数的 2.1、5.7 和 662.9 倍。我们的研究表明，中国目前采取的输入性控制措施在适当的时候实施，以防止疫情蔓延，并取得了相对较好的控制效果。然而，仍需保持警惕；否则，可能会出现另一个疫情高峰。
