A novel coronavirus pneumonia, genome wide, high-throughput sequencing and sequence analysis of 137th respiratory diseases of the new confirmed cases confirmed by the citys CDC yesterday were confirmed by the CDC of China. The sequences of the virus were identical to those of Beijings new market. Novel coronavirus pneumonia was reported on the news in Tianjin on the 146th forenoon this morning. The deputy director of the citys CDC and director of the infectious disease control room, the disease control expert, and the netizen nicknamed Holmes, Ms. Zhang Ying, introduced and interpreted the relevant information on the sources of infection of 137th confirmed cases in our city.
Three paths without clue
Zhang Ying first introduced the clues and preliminary inferences of the source of infection in the 137th confirmed case. We locked several lines, Zhang said. Whether the first case has been confirmed or asymptomatic infected, through serological and nucleic acid testing, is not found. The second is whether the contaminated food is infected, whether it is meat products, aquatic products, or some organic food using farmyard manure, which pollutes vegetables and fruits. After we collected the ingredients, we didnt find them, that is to say, we didnt find the second clue. The third clue is to pollute the environment. Is the environment he works in polluted? Then he is infected. Through our investigation, no virus nucleic acid was found in 144 samples of 18 kinds of external environmental smears.
When no clue can be found in the three paths, the investigation does not stop. The CDC has carried out a new sequencing of the virus, compared the virus with the sequencing results, and the sequencing of the genome may provide relevant clues. On August 18, the Tianjin Center for Disease Control and prevention sequenced the genes of respiratory tract samples. At the same time, on the 19th, the city CDC sent the confirmed respiratory samples to China CDC for recheck.
At the same time, on the 19th, the city CDC also did a lot of troubleshooting work. On the morning of the 19th, the city CDC collected samples of respiratory tract and blood samples from 55 chefs in the hotel for virus nucleic acid test and serum antibody test. All the nucleic acid test results were negative. Of the 55 chefs, 54 were negative, but one was positive. The center for Disease Control and prevention in the city immediately carried out an epidemiological investigation on the cook. At that time, after 137 confirmed cases were confirmed, the chef, as a close contact, had been isolated in a centralized isolation point. Zhang Ying conducted an epidemiological investigation on the chef. The investigation found that the chef had no symptoms, but the clues came. He has been to Beijing many times in the past month and has been exposed to public places in Beijing. Especially on June 8, he went to the local restaurant and entertainment center and stayed for a very long time, from dinner to midnight. Zhang Ying said that he collected the cooks respiratory tract samples and serum samples at different time points three times in a row. At the same time, he did nucleic acid test and serum test. The result of three times was still negative.
So what is the relationship between the chef and the 137th confirmed case? The city CDC immediately carried out an epidemiological investigation on chef x, and also carried out another epidemiological investigation on the 137th confirmed case, to verify their contact in daily work and life from two levels.
According to the survey, although they are colleagues, they do not have too much close contact in their daily work, that is, the general way of contact with colleagues. But there are three doubts. First, on June 10, chef X and 137 confirmed cases had a close communication of less than half a meter, and the two chatted for a while. Chef x did not wear a mask at that time, and 137 confirmed cases were wearing masks at that time.
Second, both people like to smoke. The hotel has a smoking room on the basement floor, which is a closed space without windows. The two people basically share the smoking room once or twice every day when they smoke.
Just mentioned that the whole genome of the virus was sequenced and analyzed by Tianjin CDC on the 18th and 19th, and the relevant samples were sent to China CDC on the 19th, and the sequencing results came out on the 20th. Yesterday morning, China CDC reviewed the sequencing results of Tianjin, confirmed them and sent back the confirmed report. In the confirmation report, as we saw in the news yesterday, the virus sequence of the case is exactly the same as that of the case related to the new market in Beijing. To sum up, the city CDC reached a preliminary conclusion.
It is possible that chef X may have been infected during his long stay in Beijing, especially in public on June 8. After infection, he has no symptoms and works normally. In the process of going to work, it is possible to infect the 137th confirmed case by the way of contact just mentioned.
The current investigation work is still arduous and hard. Let me give you a simple example. You all know that the room temperature is about 30 u2103. When we went to the cold storage in the market to collect aquatic products, the temperature difference in the cold storage was - 230 u2103, reaching nearly 50 u2103. With the temperature difference of 50 u2103, I have experienced a double day of ice and fire. Wearing protective clothing is very sultry. When we arrived at the cold storage, the temperature dropped sharply. At that time, the fountain pen we brought in immediately stopped coming out of the water. Zhang Ying said that even if it is hard, the investigation work has not stopped, in order to ensure that Tianjin can achieve results in this domestic interdiction war of new outbreaks. Group prevention and control, we hope to get the strong support of the society, to cooperate with us to complete this prevention and control work, to do a good job in Beijings moat, Tianjin really achieve the implementation in place, full coverage, to control the epidemic situation.
At the press conference, the reporter asked: we saw in the news on June 21 that there was a case of serological antibody positive in the screening. Is this asymptomatic infection? Is serological antibody positive infectious?
Zhang yinga: first of all, the first positive serological antibody is not an asymptomatic infected person. The management standard for asymptomatic infected persons issued by the national health and health commission refers to asymptomatic infected persons. What is the definition of one of his cases? First of all, he must have no symptoms or signs. Second, he must have respiratory tract samples. Nucleic acid test is positive. You can compare the case definition of the country, the case definition of asymptomatic infection, can you see his calculation? He doesnt count. Why? The virus nucleic acid of his respiratory tract specimen has been negative, it is only serological antibody positive, so he is certainly not the first asymptomatic infected person.
In response to the second question, is serological antibody positive infectious? Lets say that for serological antibody, it is an auxiliary diagnosis for nucleic acid detection. Therefore, only if there is the result of virus nucleic acid detection and the result of antibody, can a case be diagnosed. Otherwise, it cannot be diagnosed. So you can see that all of our suspected cases, confirmed cases, asymptomatic infections, virus nucleic acid tests are positive results. So when we diagnose a case, when we diagnose an asymptomatic patient, we dont use serological test results. But under what circumstances can serological test results be used? This time, we will check and screen the source of infection. If just infected, the nucleic acid test may be positive, but after a long time of infection, the viral load has been very small, and no nucleic acid positive result can be detected. It can only be labeled by serology. The production of serology antibody is later than that of nucleic acid, so such a window period can be compensated by nucleic acid detection. But if it is a previous infection, long-term infection, serum blood will make up for the deficiency of nucleic acid. So in the process of screening the source of infection, we are sure to use serology.
Is it infectious? Its up to us to judge in several cases. First, if he is an infected person, our serological test is very stable, and the result is very accurate. It is an acute infection, which must be infectious. Second, as you said, it is also acute, and it is infectious. Why is nucleic acid negative? So in the second case, it is possible that the nucleic acid is a false negative case. How is false negative caused? That is, it may not be infected with enough viruses to detect. Third, the nucleic acid test is negative and the serological antibody is positive, which has nothing to do with infectivity. Chef X has been intensively isolated since the diagnosis of the 137th confirmed case. The range of contact he had two days before the positive test was in the hotel, that is to say, all the possibilities that he might be infected by him have been isolated, so we dont need to worry too much.
We also remind the general public once again that low risk is not equal to zero risk. We should protect our own safety and health, pay close attention to the epidemic information, do not believe or spread rumors, understand, support and cooperate with the epidemic prevention and control work, and build a solid defense line for group prevention and control. At the same time, the citys fever clinic provides 24-hour service, and the media also publishes the waiting information every hour. Once you have fever symptoms, please immediately select the nearest hospital and the right path, and arrive at the fever clinic in the hospital once, try to contact as few people as possible, realize short process temperature measurement, detection, laboratory diagnosis, and fast centralized operation of treatment.
The reporter also asked: through this investigation, what is the inspiration for the future investigation of antibody positive situation similar to chef x?
Zhang yinga: before, we seldom used serology to tease out the source of infection, and every big data analysis can find clues. But in the early stage of the investigation, from my professional point of view, all the possibilities were basically taken into consideration, and they were also investigated, but they were not found. Previously infected chef x, without knowledge, infected 137 confirmed cases. So we only use serology at this time, that is to say, serology is helpful to identify the source of infection, can specify a direction and provide relevant clues. But it is not that every epidemiological investigation, every source of infection screening, need to use serology. Only in a few cases.