Since March, the new coronavirus has exploded worldwide. At present (April 6) has spread to 209 countries and regions, the number of confirmed more than 1.25 million. The large number of neglected “asymptomatic infections” is considered an important driver of the current situation. How can our country have any certainty about asymptomatic infected groups? In the current situation, can we hold on to the fight of war sugon in exchange for the blood-soaked struggle of countless people?
The new study says the proportion of asymptomatic infections may be 18 to 31 percent, with single-person infection equivalent to those diagnosed. However, the number of asymptomatic infections in China is not high.
When the new crown outbreak will end . . . Author’s picture
Author . . . Xu Sijia, School of Medicine, Kyoto University, Japan
What is asymptomatic infection?
Asymptomatic infection refers to a person who has no symptoms (fever, cough, breathing difficulties, etc.) but who test positive for respiratory samples of viral nucleic acids, or special antibodies in the serum. Also known as “hidden infections”.
Why do these people have no symptoms? Some people may have antibodies in their bodies soon after infection because of their strong immune system. If the amount of virus infected is small, antibodies can be removed during the incubation period, the human body will not become sick, become asymptomatic infection.
There are a few other people, the virus does not actually enter the cell to start replication. This is similar to the appearance of inanimate objects such as doorknobs and courier parcels: virus nucleic acids found in detection may come from virus fragments on the surface of human tissue.
He’s all asymptomatic infected people in the drums.
True asymptomatic infections are those who have never experienced symptoms throughout the course (incubation, morbidity and recovery). It is difficult to distinguish between people who have not yet becomeill of the incubation period and those who are truly asymptomatic.
Earlier official statistics, only clear symptoms of positive test results will be counted as “confirmed cases.” But from April 1, the official official notification of the number of asymptomatic infections, and gradually introduced corresponding measures to directly hit the outbreak prevention and control of the dead end.
The infectious power is comparable to that of the confirmed person, the actual proportion or up to 30%
In theory, because there is no severe cough, sneezing and other symptoms caused by droplet spray, this part of the infected person has less chance of spreading the virus. But by breathing calmly, the virus can also be excreted into the air, so asymptomatic infectionist people are also the source of infection, infectious.
Expression in the New Coronary Virus Pneumonia Treatment Program (Trial 7th Edition)
There is not much data on the infectious power of asymptomatic patients. A study by the Center for Disease Control and Prevention in Ningbo compared the infection rates of 30 asymptomatic patients and 161 confirmed patients, 4.1% and 6.3%, respectively. But the differences are not statistically significant, and in the case of this study, it can be understood that asymptomatic infections are close to those diagnosed.
The serum antibody test for the new coronavirus reflects the infection of asymptomatic infection sifts from another dimension:
The first encounter with the virus, the human immune response is the earliest produced IgM antibody, its appearance suggests that the infection is in the acute stage, but also the virus is more infectious stage. Subsequently, IgG antibodies appear, which is the main force to play a protective role, in the recovery period antibody titer can reach more than 4 times the acute stage, and continue in the body for several years. IgG positive indicates that the infection enters the second half of the year or has been infected, at which time the infection is relatively weak.
The production and change of specific antibody IgM and IgG in the immune response Author’s picture
Serum antibody testing not only identifies asymptomatic infections, but also traces the course of the disease. Combined with population samples, it is necessary to deduce the characteristics of virus transmission associated with asymptomatic infections. Recently, Premier Li Keqiang also called for an epidemiological sample survey in key areas of the epidemic to obtain detailed data on asymptomatic infections, including infectious capacity and duration.
As for the scale of infection, some studies have shown that asymptomatic infections account for about 18 to 31% of the total number of infected people. This group is not independent, and the trend of increasing or decreasing is consistent with changes in the overall infected population.
According to quantitative data from top research institutions, the Wuhan “sealcity” from January 23 has reduced the total number of cases of new chinese pneumonia infection in China by 96%, playing a crucial role in curbing the outbreak. If there is no intervention, the number of confirmed cases outside Wuhan may accumulate in excess of 700,000 in the 50th day of the outbreak.
At this stage, the number of newly confirmed people in China is on a downward trend, with zero growth in some provinces. It is concluded that the current number of asymptomatic infections in China is not high, and has been properly placed. As of April 6, 1033 cases of asymptomatic infections still under medical observation have been reported nationwide, of which 275 cases have been imported from abroad (the official website of the National Health and Care Commission).
How to prevent and control asymptomatic infections?
At present, screening of new coronary infections still mainly relies on nucleic acid reagents. Because the national nucleic acid testing needs to consume a lot of resources, the implementation of difficult, China’s main measures are “focus on traceability, strict lying about input.”
Active screening targets include close contacts of confirmed patients, people involved in clustered outbreaks, and people who have a history of travel or residence in areas where the outbreak is sustained. The above high-risk population will be centrally isolated for 14 days, 2 consecutive (24 hours interval) nucleic acid test, are negative before the isolation can be released. At the same time, close contacts of these people were also subjected to 14 days of medical isolation observation.
During this time, the number of new cases in the country has dropped very low, after the implementation of the above-mentioned measures, the risk of transmission of asymptomatic infections in the country is low.
The focus of the current prevention and control work is to prevent imported cases. On April 3, 18 of the 19 new confirmed cases in China were imported from abroad, and 11 new suspected cases were imported from abroad. The current outbreak is in the outbreak phase in some countries, and there is a higher risk of asymptomatic infections among the incoming population.
According to the Civil Aviation Authority, China has reduced the number of weekly international flights to about 108, equivalent to 1.2% before the outbreak. Screening at ports of entry has been further strengthened. For Beijing, Shanghai, Guangdong and other places of immigration personnel unified requirements of 14 days of isolation and nucleic acid testing.
Shanghai Pudong International Airport, district staff in charge of “from the floor to the isolation” of closed-loop prevention and control . . . Oriental Network
What can the general public do?
For the general public, the most important thing is still the cliche of personal protection: avoid crowd gathering, wear masks, wash hands frequently, indoor ventilation. If a suspected infection is found, you should assist in the reporting of information. The results of self-discipline throughout the country over the past two months have been evident to all.
Although the risk of transmission of asymptomatic infections exists, China is now on the dominant side in the control of the epidemic. The state is closely tracking suspected people with asymptomatic infections, and immigration checkpoint staff are holding their posts day and night to build health walls for us, in which case the likelihood of a second outbreak is low and there is no need to be overly stressed.
We must stick to the countless people bloody struggle to usher in the war sugon, not to let the outbreak of the resurgence of any opportunity.
(Responsible For Gao Peixuan)
1. Covert coronavirus infections can be new outbreaks. Nature. doi:10.1038/d41586-020-00822-x
2. Civil Aviation Authority: Co-ordinate international passenger flight adjustment in accordance with the law to prevent and control overseas outbreaks input http://www.caac.gov.cn/XWZX/MHYW/202003/t20200330_201811.html
3. Chen Wei, Wang Aihong, etc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4. Ho Wei. Medical Immunology (2nd Edition), Beijing: People’s Health Press, 2010
5. New Coronary Virus Pneumonia Treatment Programme (Trial 7th Edition)
6.Tian, H. et al. An i-transmission of the control measuresthe first 50 days of the COVID-19 in in China. Science (80-. . . eabb6105 (2020). doi:10.1126/science.abb6105