Fire eye laboratory technicians are performing nucleic acid detection on samples. Photo by Han Jichen
Why are "asymptomatic infections" not included in "confirmed cases"? The experts explained
On the afternoon of March 20th, the Hanjiadun Street Comprehensive Community reported on the "Important Notice" that "there was another new case in Lishui Kangcheng District last night." In response, the relevant parties in Wuhan responded: "After investigation, the residents of the community, Zhang Moumou, were asymptomatic, according to the" Notice of the General Office of the National Health and Health Commission on Printing and Distributing the New Coronavirus Pneumonia Prevention and Control Plan (Sixth Edition) " "Undiagnosed cases." So, what are "asymptomatic infections" and how big is the threat posed by asymptomatic infections? The reporter interviewed relevant experts on related issues.
What is asymptomatic infection?
According to the definition of the "New Coronavirus Pneumonia Prevention and Control Plan (Sixth Edition)", "asymptomatic infection" of the new coronavirus refers to: those with no clinical symptoms, respiratory tract and other specimens that are positive for new coronavirus pathogenicity or serum IgM antibody . In the "Pneumonia Case Surveillance Program for the New Coronavirus (Third Edition)" released on January 28, "asymptomatic infection" was distinguished from suspected cases, confirmed cases, and mild cases. Positive but without symptoms and not included in confirmed cases published daily.
Liu Youning, former director of the PLA Institute of Respiratory Diseases, said in an interview with reporters that those who have been confirmed to be "infected" but asymptomatic can be divided into two categories, one is still in the incubation period, and symptoms will occur after the incubation period, the other is Asymptomatic from beginning to end.
Why are asymptomatic infections not included in confirmed cases?
According to the definition in the "New Coronavirus Pneumonia Prevention and Control Plan (Sixth Edition)", clinical manifestations are required for suspected and confirmed cases. Asymptomatic infection patients have no clinical manifestations, and need to be isolated for 14 days and further testing is needed to make a judgment. If an asymptomatic person develops symptoms during quarantine, they are reported as a confirmed case and published.
Is a positive nucleic acid test contagious?
Both the "asymptomatic infection" and "Fuyang" patients have positive nucleic acid test results. Does it mean that the two groups are infectious? The reporter interviewed BGI on this issue and learned that a positive nucleic acid test refers to the virus's nucleic acid found at the sampling site during the test. But the nucleic acid comes from "live virus" or "dead virus", and the virus needs to be cultured to confirm. Liu Youning also said in an interview with reporters that a positive nucleic acid test cannot determine the concentration and activity of the virus, let alone whether it is infectious.
Liu Youning also said that the current "Fuyang" patients have antibodies in their bodies within a short period of time after they have recovered, and the virus cannot reproduce in them, so they are basically not contagious and are not suitable for inclusion in the category of asymptomatic infection.
How to find "asymptomatic infection" and how to deal with it?
According to the description of the "New Coronavirus Pneumonia Prevention and Control Plan (Sixth Edition)", it is currently found mainly through close contact screening, cluster epidemic investigation and source of infection investigation.
Liu Youning said that the current treatment of asymptomatic infection is to find and quarantine and report directly to the network within 2 hours. During the quarantine period, continue to conduct nucleic acid testing and further observe whether symptoms occur, and you can also use some antiviral drugs. Intervene. In principle, the quarantine can only be released after two consecutive negative nucleic acid tests.
How to tell if you are "asymptomatic"
Nowadays, the only way to confirm the diagnosis of asymptomatic infection is nucleic acid testing, but the number of nucleic acid test boxes is limited in most areas. To avoid wasting medical resources, self-diagnosis can be performed.
Guo Hongrong, director of the Department of Respiratory Medicine, Optics Valley Hospital, Wuhan Third Hospital, said that if there is no history of travel in the epidemic area, and there is no family-onset disease, no history of contact with confirmed or suspected cases, no need to worry too much. However, if you have a relevant epidemiological history, you should report it in time even if you have no symptoms, and do a good job in isolation.
Is there any asymptomatic infection in the foreign importers, and how to deal with it?
Recently, with the increase of imported cases in China, as to whether there are asymptomatic infections among imported workers, Lei Huaiding, Secretary of the Party Branch of the Department of Respiratory and Critical Care Medicine, Taihe Hospital, Shiyan, Hubei, replied: There should be some people with asymptomatic cases. Security screening is easy to ignore. The best way is to isolate and observe foreign immigrants for 14 days. "
Guo Hongrong suggested: "During the period of quarantine of returnees abroad, nucleic acid testing or genetic sequencing of people from the affected areas is performed to determine whether there are asymptomatic infections."
Reporter Cui Dong Liu Yang Wang Yuran Chen Yuanding