Wu Zunyou, chief epidemiologist of China CDC, recently wrote an article on Weibo to analyze "why do you keep identifying infected people from the control personnel and social level" He said that the repeated screening of infected people from the social level is mainly due to the following possible reasons:
First, the infected person is in the "window period" of detection, that is, he / she has just been infected with novel coronavirus. When the nucleic acid is sampled, the virus has not started to be discharged out of the body. The nucleic acid test results show that it is "negative", that is, false negative, and remains in the society. The transmission caused by him / her has formed a new infected person at the social level.
The second is missed detection. Although the screening area required by prevention and control is full nucleic acid screening, for various reasons, some people are unable to participate in nucleic acid testing. Although the "pop-up" function of security code software (limited to smartphone users) can help urge everyone to do testing, if he / she doesn't go to public places, the "pop-up" will have little impact on him / her.
The third is the sampling quality problem. When the infected person goes for nucleic acid detection and sampling, the staff's operation is not standardized, the pharyngeal swab can not be applied to the periphery of the nasopharynx, and the qualified samples can not be collected, resulting in false "negative".
Fourth, intermittent detoxification. Some infected people do not continuously excrete the virus outside the body, but intermittently excrete the virus. The infected people just did not detoxify at the time of nucleic acid sampling.
