Let's take a look at the paper published in nature medicine on June 5, 2020 about China’s latest epidemiological report on the proportion of COVID-19 antibodies in different populations in different regions of China.
The authors analyzed the antibody status of COVID-19 in the serum of 17368 people in multiple regions and found that the positive rate of serum COVID-19 antibody was 2.5% for the people with direct contact with the hospital; For those who did not have direct contact with the hospital, the positive rate of serum COVID-19 antibody was 0.8%.
This week's qPCR test results in Wuhan City, a total of 9899828 people have completed qPCR tests, no confirmed cases have been found, 300 asymptomatic infections have been found, and the detection rate is about 0.03%.
The above data gives us a clear understanding of the current situation in Wuhan. However, qPCR tests can only be used to understand the current infection status; to further understand the actual infection rate of COVID-19, it has to depend on antibodies in the blood. Because in theory, people who have been infected with COVID-19 will have antibodies against COVID-19 in their plasma, and these antibodies will exist for a long time.
Therefore, through the serological investigation of COVID-19 antibody, we have hope to know the true epidemiological situation of COVID-19.
In this study, the researchers first developed a COVID-19 N protein and S protein IgM and IgG antibody detection technology, and verified in different populations, detection of IgM and IgG specificity were 100% and 99.3%.
Subsequently, between March 9 and April 10, 2020, the researchers tested IgM and IgG antibodies on 17,368 people in four different regions of China.
Let's take a look at the data of Wuhan first. The seropositive rate of 714 medical staff was 3.8%, the seropositive rate of 346 hotel staff (the hotel where medical staff stayed during the COVID-19 epidemic) was 3.8%, and the seropositive rate of 219 medical staff members' families was 3.2%.
Let's take a look at Jingzhou and Honghu around Wuhan. The seropositive rate of 3019 medical staff was 1.3%, and the seropositive rate of 979 patients who went to the hospital for routine maintenance hemodialysis but did not show symptoms of COVID-19 was 3.6%.
In Chongqing, the seropositivity rates of 319 medical staff and 993 hospital outpatients were 3.1% and 3.8%, respectively.
In Chengdu, 9442 community residents had a seropositivity rate of 0.58%.
In Guangzhou and Foshan, the seropositive rate of 563 patients who went to the hospital for dialysis was 2.8%, the seropositive rate of 260 medical personnel was 1.2%, and the seropositive rate of 442 factory workers was 1.4%.
Based on the above data, the researchers believe that the serological test results are consistent with the early transmission of COVID-19 in China.
In addition, from the test results, although the seropositivity rate of IgG is the highest, it should be noted that some people are only positive for IgM or IgG. Therefore, the researchers believe that for serological investigations, IgM and IgG should be measured simultaneously.
The researchers also found that compared with the serum antibody test, the qPCR test of nose swabs can only detect viral nucleic acids in a very small number of human samples. Of the 23 patients tested positive for qPCR, 19 were positive for IgG and 2 were positive for IgM.
It is also worth mentioning that the researchers did not find a significant difference in seroprevalence between different genders (1.6% for men and 1.3% for women), but the seroprevalence rate was significantly higher among people aged over 65 (≥ 2.0% for 65-year-olds and 1.3% for <65-year-olds).
In summary, the above data is crucial for us to understand the overall prevalence of COVID-19 and the infection capacity of COVID-19. However, more research is needed to confirm whether these data can be extended to other regions or populations. In addition, because the population involved in this study was not obtained by random sampling, there may be a certain deviation in the seropositivity rate.
Although I have tried my best to express the content of the article, it is still not the whole content. If you are interested, please click the reference link to view the original paper.
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