Exclusive|Beijing locks in 140 hours of "Patient No. 1"
Commuting, postgraduate entrance examinations, business trips, taking care of children... As the first person to be infected in this round of the epidemic in Shunyi, Beijing, Fu Gang's life was once “outlined” by the flow of the epidemic in Beijing.
However, his infection began with an experience of shopping in a shirt shop, but the answer was revealed after Beijing CDC experienced many rounds of adjustments.
In the six days after Fu was diagnosed, 17 newly-infected patients with new coronary pneumonia were newly diagnosed in Beijing, and three areas were upgraded to medium-risk areas.
On December 30 last year, the Beijing Municipal Center for Disease Control and Prevention disclosed the traceability results of a local clustered epidemic in Shunyi for the first time-Fu Gang was infected by Chen Pingyan, a shirt shop employee; Chen Pingyan was infected by Yu Miao, an Indonesian customer.
Gene sequencing confirmed that the source of this round of the epidemic was imported from abroad and Yu Miao was the source of the epidemic.
If the cases of 16 infected people are like a tangled thread; pulling out a clear chain of transmission is like a "brain-burning" reasoning story.
Who infects whom?
In an epidemic involving many cases, there are always a few core cases, like a transportation hub, connecting upstream and downstream, and converging to the original source.
Fu Gang (the first infected person discovered on December 23 last year), Xie Yang (diagnosed on December 25, working in Chaoyang District), and Zhang Shenqiu, who were the first to get sick, were once regarded as the core of the traceability.
Ye Yan is the deputy chief physician of the Beijing Municipal Center for Disease Control and Prevention, and the person in charge of the city's disease control dispatched to Shunyi District for on-site support.
In his impression, Zhang Shenqiu is particularly prominent among the three.
The appearance of Zhang Shenqiu was somewhat accidental.
She is from Hebei, 31 years old, and works in a convenience store Shunyi District freight store.
On the afternoon of December 24 last year, she went to Dongcheng District for a nucleic acid test-not because of a history of close contact, but because the store sold cold and fresh food. The company arranged for employees to test for nucleic acid in accordance with Beijing's epidemic prevention requirements.
On December 25, Zhang Shenqiu was diagnosed. The next day, six of her close contacts were confirmed to be infected. Five of them had social relations with Zhang Shenqiu, and one had carried Zhang Shenqiu and was an online taxi driver.
Tracing the source of the flow is a bit like a puzzle. A case is a piece of small pieces. The more “pieces” that can be connected, the easier it is to form an outline.
At that time, Fu Gang and Xieyang were both isolated cases. Only Zhang Shenqiu had a clear relationship with the new case, or could provide more clues.
This group of 7 people became the focus of Ye Yan and his colleagues.
The core question to be clarified is, among the seven people, who is infecting whom?
Perhaps there is nothing more obsessed with the sequence than the flow.
Ye Yan introduced that tracing the source is a reverse reasoning. From the latest case to the initial case, the source of infection can be determined only when the order is correct.
Zhang Shenqiu is the first case among the seven people to enter the public eye. It seems reasonable to put her "upstream", but is this really the case?
"When looking for order, an important reference standard is the time of onset, but this is not easy to figure out and needs to be verified repeatedly." Ye Yan said.
The disease control personnel conducted multiple rounds of adjustments to 7 people.
Chen Yanwei, a physician in charge of the Beijing Centers for Disease Control and Prevention, participated in the supplementary investigation. She recalled that during the first round of adjustment, Zhang Shenqiu said that on December 20 last year, he had been with the case Chen Pingyan (the same township of Zhang Shenqiu, Shunyi Hualian shirt shop employee on the second floor). Had a taxi and went shopping at Wumart Supermarket in Houshayu Town, but Chen Pingyan couldn't remember.
In the first official circulation report, Chen Pingyan mentioned that he had gone shopping at Aishang Fresh Supermarket on December 20, but did not mention Wumart Supermarket.
In order to clarify the close relationship between the two, Chen Yanwei asked Chen Pingyan. After carefully recalling and searching through the payment records, Chen Pingyan remembered the matter.
The time of onset was further revised. At the beginning, Zhang Chenqiu had the earliest onset. Chen Pingyan said that she was not uncomfortable. The analyst reminded her that headaches, fatigue and other symptoms were also counted. Chen Pingyan gave a positive answer. The time of symptoms also became Earlier than Zhang Chenqiu, he became the earliest one of the seven.
After Chen Pingyan's upstream position was clarified, the communication relationship between the seven people was smoothed.
Chen Pingyan infected her husband Chen Zhi, online car-hailing drivers, and fellow townspeople Zhang Shenqiu and Chen Yue who took online car-hailing together; Zhang Shenqiu and Chen Yue also infect their husbands Chen He and Chen Ming respectively.
What excites Ye Yan is that Chen Pingyan's appearance connects Fu Gang, who could not find the source of infection.
Three branches into two
From December 23 to 25 last year, a local cluster of epidemics occurred in Shunyi. A total of 3 infected persons were found, Fu Gang, Zhang Shenqiu, and Xie Yang.
Is there a transmission relationship between the three, which directly affects the delineation of the source of infection-is it the same source or multiple sources?
Wang Xiaoli, deputy chief physician of the Beijing Centers for Disease Control and Prevention, is responsible for the traceability of the epidemic.
She recalled that in the first few days, disease control personnel had been trying to find out the close history of the three people, with little gain.
Among them, the trajectories of Zhang Chenqiu and Xie Yang did not overlap at all; Fu just had the possibility of contact with the two of them, but they could not be conclusive.
The first is Fu Gang and Zhang Shenqiu.
According to the investigation, both of them have been to Wumart Supermarket in Houshayu Town, but they did not completely overlap in time and space.
Taking into account the possibility of human contamination of the environment and the infection to humans, disease control personnel went to Wumart Supermarket for on-site sampling. The results were all negative. Repeated sampling did not find contamination. The relationship between the two was not established.
So, does Fu just have something to do with Xie Yang?
The two people lived not far apart. Fu had just been to Shunyi Hualian Commercial Building, which was very close to Xieyang’s home, less than one kilometer, but no clues were found for both of them to go there at the same time; Fu just took a bus to pass through Shunyi The district hospital is very close to Xieyang's home, but there is still no direct evidence, and the relationship between the two cannot be established.
The appearance of Chen Pingyan changed the situation.
Chen Pingyan is an employee of the shirt shop on the second floor of Shunyi Hualian Commercial Building. He went to work in the commercial building on December 17 last year.
According to Fu just stated, on December 17, he went to the first and third floors of Shunyi Hualian Commercial Building (Shunyi Store), but did not go to the second floor.
Is it so close, haven't you really touched it?
According to Ye Yan, the disease control personnel then went to the commercial building again to investigate and found the surveillance video that day, and found that Fu had just been to the second floor and stayed in the shop where Chen Pingyan worked for more than 20 minutes, which seemed to be worse than before. Without clues, this evidence is very powerful.
Fu Gang was thus associated with 7 people including Chen Pingyan.
The three "teams" merged into two, leaving only the isolated case of Xie Yang.
The last piece of the puzzle
Xie Yang "entered the team" after the asymptomatic infected Yu Miao was discovered.
Where did the virus come from?
According to Ye Yan, there are many ideas within the disease control-it may be brought by imported cases from abroad, it may be attached to cold chain imported goods, or even directly occurred locally, but they cannot be verified until Yu Miao is confirmed. .
At the same time as the adjustment, another method of traceability-whole genome sequencing is also underway.
The principle of PCR nucleic acid detection is to determine whether the sampled person is infected by comparing whether several key gene fragments of the new coronavirus can be amplified in the sample; whole-genome sequencing can thoroughly analyze the gene sequence of the new coronavirus.
There are multiple epidemic strains of the new crown virus, and the strains circulating in different regions of the world are not the same. Comparing a gene sequence with the global gene bank and finding the most similar strain sample can indicate the geographic origin of the virus.
Just after Fu tested positive, the CDC quickly collected samples of his new coronavirus for sequencing.
On December 25 last year, Wang Xiaoli got the results and found that it belongs to the European family branch 2.3 of the L genotype. It is a recently circulating virus strain in Southeast Asia, not a Beijing or domestic virus strain.
This is a piece of information that clearly prompts overseas input. After that, the disease control personnel began to look for overseas clues in the existing cases and found that the roommate Yumiao who lived with Xie Yang was from Indonesia.
Immediately, Yumiao was tested for nucleic acid and antibody. The results that night made Wang Xiaoli very excited. Although the nucleic acid was negative, the IgM antibody was positive, indicating that she was infected or had been infected.
Environmental sampling of his living space and work space also detected positive for the new coronavirus nucleic acid, confirming its detoxification.
The residence of Xie Yang and Yumiao is very close to Shunyi Hualian. Is there an infectious relationship between Yumiao and Chen Pingyan?
According to Ye Yan, further investigation revealed that Yu Miao had visited Hualian on December 13 last year and had close contact with Chen Pingyan.
This became the last piece of the puzzle, bringing together seven seemingly unrelated Xie Yang and Chen Pingyan people on the transmission chain.
The spread chain is revealed
Yumiao may be patient number one.
But was he infected before the other cases, and by whom?
Pang Xinghuo, deputy director of the Beijing Municipal Center for Disease Control and Prevention, said that although Yu Miao lives in Shunyi, he is actually an Indonesian male youth who has lived in Indonesia for a long time.
The investigation found that Yu Miao entered the country from Indonesia on November 26 last year and was quarantined in Fujian for 14 days. The nucleic acid test was negative.
On December 10, he took Xiamen Airlines Flight MF8109 from Fuzhou Airport to Beijing Capital Airport.
Wang Xiaoli recalled that after locking on Yumiao, they investigated the information on the epidemic situation in Fujian that day and found that there were indeed imported cases from abroad; they investigated only one flight from Indonesia to Fujian on the day of Yumiao's entry; and requested the imported cases from the local disease control in Fujian. The report found that Yumiao was in the same row with him, with only one seat in between.
Yumiao was probably infected by this case.
On December 30th last year, the Fujian Provincial Center for Disease Control and Prevention gave feedback on the genetic sequence of the imported Indonesian case in the same row as Yu Miao. The Beijing Center for Disease Control and Prevention found that the nucleotide similarity was 99.99%, which was highly homologous.
Based on the sequencing results, 14 cases of infected persons such as Yu Miao and 5 related environmental viruses are highly homologous, and they are the same transmission chain, and the source of infection is imported from abroad.
In addition, after Yu Miao was admitted to the hospital, the staff found a positive nucleic acid in his stool sample.
Wang Xiaoli explained that, generally speaking, the respiratory tract specimens are positive before the digestive tract specimens are positive. This clue suggests that he has been infected for some time.
Pang Xinghuo said that comprehensive investigation evidence shows that the local clustered epidemic in Shunyi District is a single transmission chain.
Yumiao was the source of the clustered epidemic. After arriving in Beijing, he spread the virus to his roommate Xie Yang, and then to Chen Pingyan during shopping.
While working, Chen Pingyan spread the infection to Fu Gang and her husband Chen Zhi, the first infected person; during gatherings, shopping, and riding in a car, it spread to fellow villagers Zhang Chenqiu and Chen Yue; during the ride-hailing ride, it spread to the driver Wang Yan.
Wang Yan was spread to Ma Wei, an online ride-hailing driver (diagnosed on December 28 last year) during the dinner together; Zhang Shenqiu and Chen Yue respectively infected their husbands; in addition, the three husbands and Chen Yue both worked in the Jinma Industrial Park. Collective activities such as co-working and gatherings caused 5 colleagues to be infected.
At this point, the entire communication chain has come to light.
The chain of transmission of the Shunyi epidemic.
Cartography/Shi Chunlei
Behind "Solving the Case"
The scale of the local clustered epidemic in Shunyi does not seem to be large. Only 16 infected people were found in 6 days. In the last round of the new epidemic, there were 36 new cases in one day.
But behind the few cases, there is a lot of front-line work.
According to Ye Yan, each case is accompanied by repeated flow adjustments, on-site sampling, and huge close contact management.
The flow report is the basis of analysis and sampling. It is rarely done at once, especially in the initial stage. There are few cases and few clues. I don’t know what information is the key. It needs to be asked in detail; new clues and new hypotheses appear later. If you need to supplement and verify the previous cases, you must ask again; when the patient's own condition is not good, the time of flow adjustment will be shortened, and the frequency will inevitably increase.
In this epidemic, some single cases have been transferred more than ten times.
On-site sampling is based on flow regulation reports.
After the initial flow report appears, the sampler will go to key points to retrieve the video, determine the close connection, and sample the environment.
As reports are updated, new cases are added, and relationships between cases emerge, a place may have to be repeated many times.
It is also not easy to manage close contacts. There are almost 100 close contacts in one case.
According to Zhi Xianwei, member of the Standing Committee of Shunyi District and Executive Deputy District Mayor, as of 12 o'clock on December 30 last year, Shunyi had tracked and checked 1,239 people who had been close contacts, all of which had been controlled.
The number of close connections is even greater.
In order to complete the investigation of these more than a dozen cases and the management of close contacts, the Beijing Centers for Disease Control and Prevention sent more than 20 people to the scene. Hundreds of people were invested in the work of traceability, testing, and information sorting. All members of the Shunyi District CDC participated. Fengtai, Daxing, Fangshan, Mentougou and other districts have also sent support personnel for disease control. Although there are no confirmed cases in some districts, they have to start management when they receive close contacts.
"There are no statistics on how many people have been invested in the disease control system, but the total number should be over 1,000." Ye Yan said.
In addition to the disease control system, the public security department, the township government of Shunyi District, the sub-districts, and the units involved have all undertaken important tasks to contribute to the traceability of the circulation and the prevention and control of the epidemic.
In addition to the imperceptible contribution, behind the cases, there are also hidden life states.
Fu just got caught up in the field of public opinion for a while, because his life was occupied by commuting, postgraduate entrance examinations, business trips, and caring for his children. Some netizens gave him the nickname "Encouragement Brother"; after several case reports in Jinma Industrial Park, his Living conditions such as working daytime, working part-time at night, and accompanying a partner also aroused emotion.
There are also worries.
"It is difficult for patients with infectious diseases to avoid discrimination." Dou Xiangfeng, chief physician of the Beijing Centers for Disease Control and Prevention, said. Will the infected person suffer social exclusion, unit treatment, and face an even worse situation?
"They are also victims. Many of their lives are not easy, and even their children can't be brought up by them. I hope they can get more understanding and kindness." Dou Xiangfeng said.
dialogue
Pang Xinghuo, deputy director of the Beijing Centers for Disease Control and Prevention: The biggest wish is to return to normalcy
Beijing News: The scale of the epidemic is relatively small. Is it easier to trace the source of the epidemic compared to when it was in Xinfadi?
Pang Xinghuo: Although there are few cases this time, traceability is still not easy.
Beijing has not had a local case of unknown origin for a long time. Everyone has a relatively relaxed mentality. There is a large flow of people and a large number of gatherings. The trajectory is very complicated; a case suddenly popped up, and the first few cases were not related, which made it more difficult. .
In the later stage, the number of cases increased and the evidence increased, and the flow adjustment gradually became clear.
The Beijing News: We found a change. The several cases from December 23 to 25 last year were discovered by accidental testing or active medical treatment. After the 26th, they were basically diagnosed in close contact. What does this mean?
Pang Xinghuo: It means that we have managed it correctly. The cases that appear in the people in charge are normal. If there are cases outside the scope of control, it means that the cases and close connections have not been found.
I didn't fight hard afterwards, and there shouldn't be any more concentrated epidemics.
Beijing News: According to statistics of the existing cases, no serious illnesses have appeared yet. The patient's condition seems to be much lighter than the previous rounds of the epidemic. Why?
Pang Xinghuo: On the one hand, it is discovered early, many in the early stage, asymptomatic, mild, and timely admission to the hospital can alleviate their symptoms; on the other hand, it is the accumulation of treatment experience. During this year, our medical institutions After a long battle, although the new crown does not have a special medicine, there are many other effective treatments.
Beijing News: What is your biggest wish now?
Pang Xinghuo: The biggest wish is to return to normalcy.
This year was difficult for everyone, and life was completely disrupted by the epidemic, and they could not move freely. Relatives and friends could not gather at will, nor could they go out for fun.
In this special period, all departments and units still need to do a good job in personnel management and epidemic prevention and control. I hope that citizens can stick to it, put the protective measures in place, and minimize the risk of epidemic spread.
(All infected persons in the text are pseudonyms)
Beijing News reporter Dai Xuan, photographer Wang Jianing