In recent weeks, several provinces, autonomous regions and municipalities have requested nucleic acid testing for people from areas at high risk of outbreaks. A major reason for this is the successive emergence of Hubei-imported asymptomatic infected persons and confirmed patients with health green codes in Guangdong and Gansu. In order to identify potential infected persons in a timely manner, Guangdong Province has requested the returnees from Hubei to take the initiative to have their nucleic acids tested at healthcare institutions. Sichuan and Chongqing have also issued similar requests. Zhang Wenhong: Nucleic acid test is one of the best means to screen for asymptomatic infections In a group of people infected with the new coronavirus, some of them are destined to develop fever, cough, pneumonia and other symptoms, but some do not have the disease or the symptoms are very mild, and these are asymptomatic infected people, but their nucleic acid test will still be positive. Therefore, nucleic acid testing has become an important tool to detect these asymptomatic infected people. Zhang Wenhong, director of the Department of Infection at Huashan Hospital of Fudan University, said the health code can only tell you that they have done some preliminary screening. In fact, there’s no way to screen for asymptomatic infections in the first place. So this is not to say that the health code is a loophole, just that the health code has a blind spot for screening. I’m in favor of health codes because they cover most of the case finding. What about the small number of asymptomatic infections that are missed? We have to set up some other mechanisms, now the best technical means of screening asymptomatic carriers, nucleic acid testing should be considered one of them. Liu Tong, a young man from Hubei province, was sent here for a free test immediately after arriving at the integrated service point in Yuecheng district, Shaoxing, Zhejiang province, on Wednesday. Liu Tong will be tested for nucleic acid by collecting a nasopharyngeal swab. Nasopharyngeal swabs and oropharyngeal swabs are two commonly used methods of nucleic acid testing. Accompanied by nausea, coughing and other discomforts of the tested person, the swab extracts the test substance in contact with the mucous membrane of the nasopharynx or oropharynx. Zhang Wenhong: The virus can not be seen or touched, and now the only thing that can be detected is the gene of the virus. Scrape inside the mouth, scrape in the nose, you can in a machine to the viral genes, as long as the positive is certainly there. So nucleic acid testing is very significant for screening asymptomatic infected people. After a night’s stay at the integrated service point, Liu Tong waited for the result of a negative nucleic acid test. Zhang Wenhong: China does not yet have a large number of asymptomatic infected people on its soil As nucleic acid testing has been stepped up in different parts of the country, the number of notifications of asymptomatic infected people is increasing cumulatively. However, in Prof. Zhang Wenhong’s view, asymptomatic infections must be accompanied by symptomatic confirmed cases, and the number of confirmed cases in China has not increased but rather declined, which suggests that there is not yet a large number of asymptomatic infections in China itself. The screening of asymptomatic infected people must be emphasized, but there is no need to over-interpret. Zhang Wenhong: Without many symptomatic people, the number of asymptomatic infected people is limited. The number of symptomatic infected people is still small, Shanghai has not had a local case in the past month. If there are no local cases for a month in a row, I think the number of cases of asymptomatic infected people in Shanghai is also 0. There are still some areas in the country that have a stock of asymptomatic infected people, and if these stocks over time, after two more incubation periods, there are still no local confirmed cases across the country, then the concept of the asymptomatic infected people is slowly becoming unimportant. Zhang Wenhong believes that the domestic asymptomatic infected people caused by the relatively low risk of transmission, in contrast, due to the surge of the epidemic overseas, foreign imports of asymptomatic infected people to China, if not strictly screened and tracked, the risk of community transmission is much greater. Zhang Wenhong: Epidemiological incidence abroad is now much higher than Wuhan, the United States, New York, there are more than 20 million; Russia, a flight down, 10% to 30% positive rate. So now the importation of foreign countries to increase screening efforts is a very scientific strategy. Zhang Wenhong: a nucleic acid test false negative rate of about 30% This week, Beijing notified an outbreak of overseas importation of associated cases caused a high degree of concern. An international student arrived in Beijing for 14 days of quarantine and underwent three nucleic acid tests, all of which were negative, but was diagnosed five days after he returned home from quarantine and infected three family members. In Zhang Wenhong’s opinion, the international student was a typical case of asymptomatic infection before diagnosis. The reason why the three nucleic acid test did not find, because the nucleic acid test there is a certain false-negative probability. Zhang Wenhong: a nucleic acid test, false negative rate should be 30%, false negative rate with what? What does the false negative rate have to do with? Whether or not the sampling was done properly, and how sensitive the test is. But if I do it again I can increase the sensitivity and the false negative rate can be reduced to 10%, so it’s a very low probability event. There was a loophole through rigorous screening, and the defense has to continue to be strengthened if we want to prevent this from happening again. Zhang Wenhong: the epidemic is unlikely to end in a short period of time, the epidemic will become normalized Zhang Wenhong believes that the pressure of foreign input will continue to exist, the epidemic in a short period of time seems to have been impossible, the medical system around the world to always maintain a strong sensitivity, vigilance and rapid response, and for the general public, may have to learn to get used to the normalization of the epidemic, while going to work, while the fight against the epidemic. ZHANG Wenhong: Many people now think that there should be not a single case before they can go back to normal life. I’m telling you, don’t dream, this life is not normal because the world is now in a pandemic. Don’t be surprised if there are one or two cases now and then, we need to start a normalized fight against the pandemic. For a long time our focus should be on a rapid return to normal life, to study, to work and to restore the economy. It only makes sense that once in a while a new coronary pneumonia patient comes out and we treat him off quickly. Source: CCTV News