Experts explain xi'an multi-round nucleic acid: the virus has an incubation period When sampling, no detoxification may not be detected

Author: People's Daily Health Client Wang Zhuo

Starting at 8 o'clock on December 29, Xi'an City, Shaanxi Province, launched the sixth round of nucleic acid testing for all employees in the city. According to the data of the seventh national census, the permanent population of Xi'an is about 12.95 million, which means that the cumulative number of nucleic acid tests in Xi'an will exceed 70 million.

How many nucleic acid screenings are needed in Xi'an during this round of the epidemic? Zhang Boli, an academician of the Chinese Academy of Engineering, explained in an interview with the People's Daily health client: "The number of large-scale nucleic acid tests during the epidemic needs to be decided based on the progress of the epidemic and the comprehensive analysis of the test results, and it is still difficult to estimate. ”

Data chart Photo by Cao Zihao

At the press conference on the prevention and control of the new crown pneumonia epidemic in Xi'an on the afternoon of the 29th, it was announced that a total of 5,077 sampling points were set up in the city, 30,900 sampling personnel were invested, 132,900 service support personnel were put in place, and more than 1,200 mobile sampling teams were established. In addition, it is necessary to conduct roving sampling of people living in construction sites, shops and stalls, and to sample special persons who are bedridden and have limited mobility.

The overall sampling speed of this round of nucleic acid testing has been shortened from the initial 10 million people in 24 hours to 7 hours; the sample transfer efficiency has been shortened from 8 hours for laboratory batch sampling to 4 hours; the results have been shortened from 30 hours for 3 million people to 12 hours; and the maximum daily screening capacity of the city has increased from 700,000 tubes per day to 1.6 million tubes.

At present, Xi'an has added more than 150 new people for 4 consecutive days, and the population base is huge, and it is difficult to screen out all hidden infected people with only a few rounds of nucleic acid testing.

In response to the reasons why Xi'an will carry out multiple rounds of nucleic acid testing, Wei Xiaoli, deputy director of the Xi'an Municipal Center for Disease Control and Prevention, once explained that first, because the new crown virus has a certain incubation period, a small number of infected people have intermittent detoxification, and sampling is only a time point, if the sampling is not detoxified or the virus concentration is not enough at that time, below the detection limit, it may not be detected.

Second, factors such as the depth of throat swab collection during sampling, the location and the time when the throat swab comes into contact with the mucous membrane will also affect the accuracy of the results. If the sampling method is not standardized, the appropriate part cannot be collected, which may cause missed detection.