Why are cases diagnosed after 2 negative nucleic acids? Wu Zunyou responded

BEIJING, July 1 (Chen Hang) Beijing Municipal Government Information Office today held the 138th regular press conference on epidemic prevention and control, for patients with two nucleic acid test negative after diagnosis of the problem, China's Center for Disease Control and Prevention chief epidemiologist Wu Zunyou said that the current nucleic acid testing and antibody testing is to check the body two different components, the former detection of viral nucleic acid, the latter detection of antibodies. Testing nucleic acids is checking the nasopharyngeal part for viral nucleic acids. If it is positive, there is an infection. Antibodies are substances that reflect the body's immune response to viral infection, usually two weeks after infection, not an infection can be detected antibodies, but from two different angles to reflect the status of the infection.
Wu Zunyou, the individual early no antibodies, antibodies test negative is very normal. Nucleic acid testing later negative, the possible reasons are as follows: First, the virus infection in the lungs, now sampling is usually in the nasopharyngeal or pharynx, lesions produced secretions to block the respiratory tract of the lungs, the amount of virus in the pharynx is very small, at this time may not be able to pick up. Second, sampling is not in place, the quality is not high. Third, the patient infected with the virus after the disease changes, and sampling period will affect the quality of sampling.
Wu Zunyou said that the above three conditions may cause test negative, and later confirmed, this situation is generally clinical, but relatively rare. This involves interpreting laboratory test results. For a person who has been in contact with a patient, or has been to a high-risk area, and has symptoms, even if the nucleic acid test negative can not be taken lightly. At this time can not only rely on nucleic acid detection, to be combined with epidemiological history, clinical symptoms to see. If a person does not go to a high-risk area and does not come into close contact with the infected person, nucleic acid testing negative is safe.