"Early detection, early reporting, early isolation, early diagnosis, early treatment" close contacts is the first line of defence for infectious disease prevention and control, and effective prevention and control of accurate tracking investigation, home visits, health monitoring, home isolation, centralized isolation, etc, measures will effectively contain the spread and spread of the epidemic. According to statistics, there are more than 2,000 "three-person groups" in Guangzhou, with more than 5,000 police officers. They are also equipped with corresponding cadres and doctors of the neighbourhood committees, it has achieved full coverage of all communities, making important contributions to the accurate isolation of close contacts, the control of the source of infection and the cutting off of transmission routes in Guangzhou . As of March 31, the turn positive rate of close contacts (local cases + nonlocal cases) was 2.72% (246/9036) in Guangzhou. The Beijing Health Commission announced that the rate of turn positive of close contacts in Beijing is about 5.8% . Guangzhou is almost half less than Beijing. One of the reasons is to find close contacts in time; the national close contact tracking coefficient is 8.68 (707913/81554) , Hubei province is 4.1 (278179/67802) , the epidemic epicentre Wuhan has not announced the number of close contacts. The tracking coefficient of local case close contacts in Guangzhou has risen linearly since February 4. The higher the tracking coefficient, the greater the tracking strength. As of March 31, the tracking coefficient reached the highest 14.2, which is higher than the national average, indicating our tracking strength It is constantly strengthening, and the close contact investigation in Guangzhou is more effective.
However, the close contacts involved in the COVID-19 epidemic came from all over the country. There are many close contacts, and there are many tracking investigation official letters requested. All the tracking investigation official letters are sent and received in the form of official letters from government departments and administrative institutions (CDC). The process is cumbersome and involves much staff, and the opaque information also affects the tracking time of close contacts. For example, Guangzhou sent and received an official letter of inquiry through at least four departments and 15 people. The opaque information also caused different cities to send letters repeatedly, wasting a lot of manpower and time. Close contact has complained that he received more than 10 calls from different departments and cities asking him about his status at the same time. At present, with the spread of the epidemic in the world, many overseas Chinese, Chinese, and international students choose to return to the country to avoid an epidemic. the number of imported cases of foreign flights increased, and more and more people from all over the country asked for assistance to check the close contacts of flights, but the communication often lacked information, such as close contacts of the Paris-Guangzhou flight CZ348 were requested to provide only the passport number. For example, a positive patient in Shenzhen took a taxi to leave Guangzhou Baiyun Airport. When Shenzhen CDC sent a tracking investigation official letter to the Guangzhou CDC asking to track down the taxi driver and provide only the taxi license plate. Due to the lack of sharing mechanism between the public security department, health department and transportation department in the same city, the information cannot be transferred and shared. Each time the Guangzhou CDC encounters an inquiry letter with unknown information, it needs to send a tracking investigation official letter to these departments. It usually takes a few days to get the relevant results. After receiving the information, the Guangzhou CDC is forwarded to the district CDC according to the territory, which greatly reduces the working efficiency of close contacts tracking investigation. At present, there is no shared system for close contacts tracking and investigation in the country. The close contacts tracking investigation lacks a unified standard, and the tracking investigation depends to a large extent on local understanding and practice; big data platforms in different cities and different departments are often self-built and strictly Restricting the authority of the platform, the lack of information sharing; the lack of communication and cooperation between cities makes it difficult for close contacts to share information.
China is a country with a large population and strong population mobility. It is unrealistic to rely on the health department to tracking and investigate close contacts alone when encountering major epidemics involving all parts of the country, many levels and many personnel. Now is the Internet era. Networks, computing, software, and data are everywhere. Big data, or huge amounts of data, is the ability to quickly obtain valuable information from various types of data.. In this COVID-19 epidemic, some cities use big data to track the life trajectory of close contacts, population exposure history, lock down the source of infection and close contact with the population, to provide valuable information for epidemic prevention and control. For example, the big data administration of Zhengzhou uses technologies such as big data and artificial intelligence to open up the sharing channel of epidemic data among all departments of the city, and accumulatively collects 16 million pieces of data of 42 categories such as confirmed personnel information, suspected personnel information, close contacts information and traffic information of the city. The Haidian District Government of Beijing has assembled personalized data analysis. For key personnel, high-risk suspected personnel, and close contacts, according to the requirements of the Beijing Municipal Health Commission's classification and prevention and control requirements, a daily collection of key physical signs indicators, and tracking and processing of recorded information [18 ]. Big data brings new methods and technologies so that the original large-volume, time-consuming and labour-intensive work can be sorted out by big data technology, and the working method becomes faster and more efficient. It is suggested that the government take the lead to clarify the information classification of close contacts and the responsibilities of each department, determine the population information Shared with relevant departments in the form of system, and improve the information-sharing system of close contacts to achieve information interconnection and sharing (Fig. 4).