After the third round of nucleic acid screening in Huinan, Pudong, what was the reason for the closure of all communities in Youjiang on the 25th?

Wu, director of the Municipal Health and Wellness Commission, said that the key areas were determined according to the comprehensive factors such as the cases and infected persons since the outbreak, their gathering and distribution characteristics in regions, units and people, and taking into account the population density, social characteristics and economic activities of the region. This time, in principle, streets (townships) are taken as screening units, and the scope of key screening areas is delineated. After completing the nucleic acid three times in this round, the infection risk of people in the screening area is comprehensively judged according to the screening results, and whether there is a risk of diffusion and transmission. After the verification results come out, we will dynamically adjust the next epidemic control measures according to the number of cases and asymptomatic infected people, age distribution and population distribution in this area, especially in combination with epidemiological investigation.

The process of screening management and control is dynamic. Closed-loop management usually starts in two days, but the situation may change during the management process. For example, once the nucleic acid test results of quality control personnel are abnormal, it may be necessary to adjust the locations and personnel involved and carry out "upgrade management". Different situations lead to the corresponding extension of the control time of the involved places and controllers.

It is suggested that those who have completed the screening should try not to go out if there is nothing particularly important, so as to avoid the large-scale flow of personnel during the screening to the greatest extent. Wu, director of the Municipal Health and Health Commission, said that screening in key areas involves people. "Personal safety" and "regional safety" are two levels. On a personal level, if all three tests are negative, it means that you are relatively safe at present. From the regional level, only all the people in this area were negative in the second screening, suggesting that the risk in this area is relatively small at present. If positive cases are detected in this area, especially in the case of a large number of positive cases, it shows that there are still potential risks of infection and transmission in society, and further research is needed to take targeted prevention and control measures.