Question and answer on the results of the national serological epidemiology survey of neo-coronary pneumonia

, the CDC has completed a national serological epidemiology survey and analysis of neo-coronary pneumonia. The purpose of this survey is to understand the new coronavirus infection situation of the general population in different endemic areas of neo-corona pneumonia, to deepen the scientific understanding of the characteristics of neo-coronary pneumonia infection, and to assess the effectiveness of epidemic prevention and control in China.
Survey covers three types of areas, including Wuhan City, Wuhan City, Hubei Province, and six provinces outside Hubei (Beijing, Liaoning, Shanghai, Jiangsu, Guangdong and Sichuan), using a sample survey design to select more than 34,000 people in the community, through the detection of serum new coronavirus antibodies, estimated the level of infection of the new coronavirus in the population. The survey was conducted using cross-sectional survey method, and the investigation was conducted one month after china had contained the first wave of neo-crown pneumonia. The survey found that the positive rate of new crown antibodies was 4.43% in the community population in Wuhan area, 0.44% in Wuhan, Hubei Province, and only 2 cases of antibody positive were detected among more than 12,000 people in six provinces outside Hubei Province. The antibody-positive rate of people who have been exposed to confirmed cases of neo-coronary pneumonia is significantly higher than that of other groups, and the antibody-positive rate of middle-aged and elderly groups is higher than that of other age groups.
results show that the population of our country is at a low level of infection, indicating that the control of the epidemic in Wuhan as the main battlefield has been successful and effectively prevented the spread of the epidemic on a large scale.
to facilitate public scientific awareness of this serum epidemiology survey, the Center organized the relevant experts to write the following questions and answers.Serological epidemiological investigation is an epidemiological survey conducted by serological methods and techniques, through the analysis and study of the distribution law of specific antigens or antibodies in the serum of the population and its factors, to clarify the occurrence and prevalence of infectious diseases, to evaluate the effectiveness of vaccination and so on.
This new coronary pneumonia serological epidemiological survey is a month after China curbed the first wave of neo-crown pneumonia outbreak, in representative areas of the cross-sectional survey, through representative sampling in the population, serum samples collected for antibody testing, to understand the level of infection of the new coronavirus in the population., after the new coronavirus infects the human body, the replication of the virus in the body can stimulate the body to produce specific antibodies, antibodies often last longer. The new coronavirus-in-the-body antibody inhibits virus replication, thus protecting the human body. New corona-specific antibodies have been detected in the body, indicating that the new coronavirus may have been infected in the past.Through certain sampling rules in the target population to select the subjects for new coronavirus antibody testing, the positive rate of antibody in that population can be calculated, in the case of no vaccine, reflecting the accumulation of new coronavirus infection rate in the population over a period of time.serological survey is based on the community population as the object, using a good sampling design, the population representative is better. Antibody detection uses a variety of reagents in-half initial sieve, followed by cell micro-neutration test review detection strategy, to maximize the sensitivity and specificity of the detection strategy.this survey is the first large-scale new coronary serum antibody-positive rate survey based on population in different endemic levels. National representative surveys conducted in other countries have found that, after the first wave of epidemics, infection rates are generally low. A two-stage random sample conducted in Spain from 27 April to 11 May found that the national average serobody-positive rate ranged from 3.7 to 6.2 per cent. A follow-up study conducted in Switzerland from 6 April to 9 May on the national population queue found that the antibody-positive rate at the fifth week was about 11 per cent.1 survey has different purposes
The purpose of the serological epidemiology survey is to understand the past infection status of the new coronavirus in the population, while the purpose of mass nucleic acid screening in the population is to search for people who have found an existing virus infection.
2 detection methods are different
Serum epidemiological investigation is to detect the level of antibodies in the serum of the new coronavirus, and large-scale nucleic acid screening in the population is the use of PCR method to detect the new coronavirus nucleic acid fragments.
3 results have different meanings
the detection of specific antibodies (i.e. antibody-positive) in the human serum indicates that they are previously infected, and if the nucleic acid results are negative, the virus has been removed from the body of the previously infected person and is not contagious. If nucleic acid test positive, regardless of the antibody test results, indicates that the individual may be in a toxic state, is a potential source of infection, especially in the late incubation period and acute period of high viral load infection, indicating the need to isolate or treat it to prevent the spread of the virus.
(Source: CDC New Crown Pneumonia Prevention and Control Technology Group)