Epidemiology expert Wei Sheng: It is
not appropriate to use the antibody positive rate to measure the current asymptomatic infection
Yangtze River Daily News (Reporter Huang Qi) Recently, some netizens used the reported antibody positive rate in Wuhan to calculate the number of asymptomatic infections in Wuhan, causing misreading by some netizens. In fact, the results of the 11,000 residents' serum epidemiological sampling survey conducted in Wuhan in mid-April have not yet been announced.
Regardless of whether the antibody positive rate of the population used by netizens is true or not, is it scientific to infer the number of asymptomatic infections in Wuhan? In response, a reporter from Changjiang Daily interviewed Wei Sheng, a professor at the School of Public Health of Tongji Medical College of Huazhong University of Science and Technology.
Professor Wei Sheng said: "Nucleic acid detection is currently the main method of diagnosis of new coronavirus infection. Direct detection of specific sequence fragments of the virus to determine whether new coronavirus is infected. If the test result is positive, it indicates that the subject is currently in the infection state. . "
The serological sampling survey of 11,000 people conducted in Wuhan in mid-April is to determine whether the new coronavirus has been infected by detecting whether there are new coronavirus-specific antibodies in the human body. Wei Sheng introduced that, generally speaking, after the human body is infected with the virus, the immune system will produce two antibodies, one is the IgM antibody, which appears earlier and disappears faster after the human infection, which is an indicator of recent infection; the other is IgG Antibodies, which appear later than IgM and last longer, are indicators of past infections in humans. The serology was conducted in Wuhan in mid-April, because the diagnosis was carried out after the confirmed cases were cleared, and the level of antibody obtained was estimated to reflect the level of IgG.
Wei Sheng believes that because the results of the serological sampling survey of 11,000 residents in Wuhan have not been announced, it is currently impossible to know the infection status of the population in Wuhan at that time. Even if the infection status at that time is known, it cannot be used to calculate the existing asymptomatic conditions in Wuhan The number of infected persons. After all, the infection status of the population is dynamically changing. People with asymptomatic infections will not be in a state of asymptomatic infections forever. Over time, most people with asymptomatic infections will heal.
"If the IgG antibody positive rate is low, it means that the prevention and control measures have prevented most people from being infected with the new coronavirus; and if the IgG antibody positive rate is high, it is not a bad thing. This may have a certain effect on preventing the human body from being infected with the new coronavirus." Wei Sheng said.
At the same time, according to the results published earlier, only one case of nucleic acid positive was found in the nucleic acid test conducted in Wuhan during the same period, indicating that the proportion of Wuhan residents who were infected at that time was less than 1 in 10,000.
He believes that the current centralized nucleic acid testing in Wuhan is mainly aimed at screening asymptomatic infections as soon as possible and performing isolation observation to minimize the possible transmission risk. These measures can further reduce the level of infection in the population and increase the public's sense of security.