Home World The ins and outs of the discovery of more than 100 cases of asymptomatic people in Kashgar, Xinjiang, can be seen behind the effective control of the epidemic in the Mainland: scientific tracking of national testing | Blog Post

The ins and outs of the discovery of more than 100 cases of asymptomatic people in Kashgar, Xinjiang, can be seen behind the effective control of the epidemic in the Mainland: scientific tracking of national testing | Blog Post

by news dir

October 28, 2020 11:34 Last Update: 11:37

After the fall, a cluster of epidemics occurred in the Mainland for the second time in just two weeks. In Kashgar, Xinjiang, a hundred new cases of asymptomatic infection have suddenly been added in recent days. Outsiders are speculating whether the second wave of epidemics in autumn and winter has struck?

The outbreak in Xinjiang started with a 17-year-old girl working in a factory. She was found to be an asymptomatic infected person during the “examination required” on the 24th. The local area quickly tested the close contacts, and then further tested the people in Shufu County, Kashgar Prefecture, where the infected person was located, and then expanded to Kashgar. As a result, more than 100 cases of asymptomatic patients were quickly found across the region.

Experts also carried out a scientific analysis of the source of the disease and found that the nucleic acid test of the garment factory where the 17-year-old woman was located was all negative, and the 137 positive patients announced on the 25th were all related to the factory where their parents were located. The infected person was the first close contact of the object found Close contacts of the patient, this shows that they had a source of infection before the 17-year-old woman. It cannot be ruled out that his workers are not infected, and it is possible that some workers have just been infected and have not yet tested positive.

Based on these data, Jiang Qingwu, a professor at the School of Public Health of Fudan University, believes that if there are only one and two generations of cases, so many positive cases will not be detected. There may be three generations of cases, and the first confirmed 17-year-old woman is likely It is a third-generation case.

In the latest news, as of 5 pm on October 27, 4,746,500 people in Kashgar have all completed nucleic acid tests. Except for 183 people in Shufu County that have been reported to be positive, the rest are all negative. It can be said that it was precisely because of an expanded “examination and inspection” that a large wave of asymptomatic infections were found when the epidemic was in its early stages. Subsequent local response and national testing, the entire process was very efficient and scientific, and the epidemic was quickly contained within a few days.

Many experts believe that as long as all the close contacts of the suspicious patients discovered first are found, quarantined, and timely prevention and control measures are taken, the epidemic is basically controllable. At present, the focus of epidemic prevention and control in the Mainland is still to manage imported cases and interrupt the related spread of imported frozen food chains. To do well in these two aspects, the possibility of a second wave of epidemics in autumn and winter is relatively small.

Since the beginning of autumn, China has experienced a cluster of epidemics for the second time in just two weeks.

Within two days, there were 164 new nucleic acid-positive cases in Kashgar, Xinjiang, all of whom were asymptomatic.

The new crown virus is worthy of being the most powerful enemy of mankind in a hundred years. Its cunning lies in that it can always find a gap, escape the strict prevention and control system, and hit people head-on in an unexpected way.

On October 24, Kashgar, Xinjiang, detected an asymptomatic infection that seemed unremarkable and could occur in any city.

On October 25, Fengyun Mutant, in the nucleic acid test of a total of 422 close contacts of this asymptomatic infected person and close contacts of close contacts, it was found that 137 of them were nucleic acid positive, and all of them were Asymptomatic infection.

On October 26, Shufu County, Kashgar Prefecture, where 138 asymptomatic infections are located, completed a national nucleic acid test for 245,200 people, and 26 new cases of asymptomatic infections were added (another 5 mixed test bottles are being retested) , The rest are negative results.

Why are 164 cases of asymptomatic infections?

The most striking thing about this epidemic is that all 164 cases detected so far are asymptomatic infections.

The first case of infection was a 17-year-old girl who worked in a factory. Her life track was simple. Most of the time she went back and forth between home and the garment factory where she worked. She occasionally visited the mall and visited the local factory where her parents worked. No history of foreign travel, no history of exposure to feverish persons.

She was discovered during a “due checkup”. In June, the National Health Commission announced 8 key groups of people who need a “due checkup”: close contacts, overseas immigrants, fever clinic patients, and new hospitalized patients And escorts, medical institution staff, port quarantine and border inspection staff, prison staff, and social welfare and pension institutions staff.

According to this definition, factory employees do not seem to be included in routine nucleic acid testing. However, after the Xinjiang region experienced an epidemic of more than 500 confirmed cases in August, the scope of “exhaustive examination” has obviously expanded a lot. Therefore, this 17-year-old girl working in the factory was also included in the scope of “should be checked.”

It was precisely because of an expanded “should check all checks” that a large wave of asymptomatic infections were discovered when the epidemic was in its early stages.

“The 164 cases are all asymptomatic, indicating that the development of the epidemic is still at a relatively early stage.” Jiang Qingwu, a professor at the School of Public Health of Fudan University, said to 8:00 Jianwen. Then the epidemic may have spread when it is discovered.”

Professor Lu Hongzhou explained in more detail the reasons for judging that the epidemic is at an early stage.

“Asymptomatic infections are divided into two situations. One is that the truly asymptomatic infections never have symptoms; the other is that they are in the early incubation period of the virus infection. A few days later, the symptoms will start after the onset period.”

“Because of this early discovery, there are people who have not yet shown symptoms, and the proportion of asymptomatic infections is surprisingly high, but a few days later, some of the current asymptomatic infections may turn into confirmed cases.”

Although Professor Jiang Qingwu judges that it is in the early stage of the epidemic, from the scale of the infection, Professor Jiang Qingwu believes that if there are only first and second generation cases, so many positive cases will not be detected, and there may be three generations of cases. The first confirmed 17-year-old woman is likely to be a third-generation case.

The so-called intergenerational division of cases can be understood as if A infects B and B infects C, then ABC is one, two and three generations of cases respectively. Jiang Qingwu analyzed that the nucleic acid test of the garment factory where the 17-year-old woman was located was all negative, and the 137 positive patients announced on the 25th were all related to the factory where her parents were located. The infected person was the first close contact of the object to be found. Close contacts, this shows that they had a source of infection before the 17-year-old woman. It cannot be ruled out that his workers have not been infected. It is also possible that a worker has just been infected and has not yet tested a positive result, so it will take a few days to repeat the test.

Similar to the strains circulating in Central Asia and Eastern Europe?

Of course, our understanding of a new virus is always limited. The scientific community has not yet concluded the proportion of asymptomatic infections and transmission capacity of the new coronavirus.

Professor Liu Youning, a well-known respiratory expert and the seventh chairman of the Chinese Medical Association Respiratory Diseases Branch, believes that the reason why these patients have a large proportion of asymptomatics is mainly related to the virus strain, and most patients may not have clinical symptoms in the future. which performed. Serum antibodies should be measured. If some patients’ lgm has disappeared and only lgG remains, they may have been infected for a long time.

According to Liu Youning, asymptomatic infections account for a large proportion of the people infected in Russia, Belarus, and Central Asia. According to Liu Youning, more than 40% of Russian patients are asymptomatic infections, and even higher in Belarus. The data in the previous paragraph is close to 80%.

Based on this, he put forward a speculation whether the virus strain this time is similar to the strains in Central Asia, Eastern Europe and other countries.

“This is my suspicion, especially when Kashgar and Central Asia and Eastern Europe where the epidemic occurred are relatively close. Of course, I have no evidence yet. Now our top priority is to find out whether it is imported or local through epidemiological investigation and traceability. .”

Geographically, Kashgar, Xinjiang is located on the western border of China, bordering four countries in Central Asia, with a border line of 388 kilometers.

Professor Lu Hongzhou believes that the Kashgar epidemic can be judged as a cluster of imported cases under the premise that there is no local epidemic in China. The “early detection link” of the epidemic can be scored high, but how to strictly control imported cases and do a good job in closed-loop management to prevent the occurrence of clusters of cases will be normal work in the future.

“The prevention and control of air ports has been done well. I have always worried about land ports. Xinjiang and Yunnan have long land ports. The epidemic in Europe and America is still spreading, and the epidemic in Southeast Asia is also spreading. Clusters of imported cases are difficult to avoid.”

The dilemma of infectious disease prevention and control in a small border town

It is worth noting that the 164 asymptomatic infections currently detected are concentrated in Shufu County in Kashgar. Statistics show that Shufu County is a place with a higher mortality rate from infectious diseases.

In a paper co-written by the Shufu County Center for Disease Control and Prevention and Guangzhou City Center for Disease Control and Prevention, it is mentioned that Shufu County is located in southern Xinjiang and the local climate is prone to cause infectious and endemic diseases.

In Shufu County, tuberculosis is a more common infectious disease with a high mortality rate. In 2017, the standardized death rate of tuberculosis among residents of Shufu County was 103.45 per 100,000, much higher than Xinjiang and other places in the country.

Zhang Yanping, the second station director of the Southern Xinjiang Workstation of the China Centers for Disease Control and Prevention, wrote in an article that from March to May every year, wind and sand will hit Kashgar. In order to prevent sand, the windows of many villagers’ houses are repaired few and small, and the air circulation is not smooth. Poor natural weather conditions and other factors, coupled with the residents’ lack of awareness of infectious disease prevention, make the prevention and control of tuberculosis more difficult, and the clustering of tuberculosis families and villages is obvious.

Similarly, the above-mentioned various disadvantages are also difficulties in the prevention and control of the new crown epidemic.

Chang Rongshan, a virology expert at Shantou University, said that the epidemic of tuberculosis will make the prevention and control of the new crown epidemic more difficult:

The western and southwestern border areas have a high incidence of infectious diseases. For example, there are 32 kinds of epidemic diseases in Xinjiang. Tuberculosis and AIDS have a higher infection rate than the mainland. Tuberculosis patients are more likely to be infected because tuberculosis takes a long time and the immune system declines severely. It is easy to be infected by respiratory pathogens.

In such an area with severe tuberculosis, it is more important to complete all staff testing as soon as possible to control the epidemic, because if it is infected with tuberculosis patients, it may not only accelerate the spread of the epidemic, but also cause more harm to tuberculosis patients.

There are two epidemics in two weeks, did the second wave of the autumn and winter epidemic really begin?

The current prevailing view is that the Kashgar epidemic is related to the fall in temperature in autumn and winter.

Not only the new crown, autumn and winter have always been the seasons for high incidence of respiratory infectious diseases. Especially in the past two weeks, the two consecutive outbreaks in Qingdao and Kashgar have made people worry, is it not just Europe and the United States. With the advent of autumn and winter, will China’s second wave of epidemics begin?

However, many interviewed experts believe that season and temperature are not the key to the spread of the epidemic. The new crown virus has no obvious seasonal dependence. Even if it is influenza, there is a peak of transmission in summer.

Professor Lu Hongzhou, an infectious disease expert at the Shanghai Public Health Clinical Center, explained that the virus is more likely to survive longer in the external low temperature environment in winter. This is a secondary factor. The most critical factor is that due to the low temperature, people are likely to be in closed doors and windows. In the environment, infection caused by close contact between people.

In other words, human behavior is the main determinant that makes the virus easier to spread in autumn and winter.

From this perspective, even in autumn and winter, the epidemic can be effectively prevented.

Professor Liu Youning believes that since the local virus basically does not exist anymore, as long as we manage the imported patients and block the related spread of the imported frozen food chain, there will be no second wave of pandemic in the fall.

Lu Hongzhou also holds the same view-China is unlikely to have a second wave of epidemics. The current epidemic is only sporadic. As long as the current normalized prevention and control is adopted, there is an epidemic. We will find it the first time and track it through big data. Isolation and nucleic acid testing of all employees can completely control the epidemic and eliminate it completely.

At present, in addition to Shufu County, which has completed all staff inspections, half of the daily inspections of 4.74 million people in Kashgar have been completed, and the rest is expected to be completed today.

“So under the current situation in China, as long as we maintain a normalized prevention and control measure, we can still detect possible clusters of cases, and we can still control the epidemic at an early stage without causing the so-called first The second wave of epidemics.”

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