Expert Answer: Why the wholesale market is easy to become an outbreak point

June 13th, Beijing announced four new confirmed cases of new crown pneumonia, with the trajectory pointing to the same place, the wholesale market for agricultural products in Xinfa. At the same time, the new coronavirus nucleic acid was detected in the new market practitioners and environment.
Beijing, which has not reported new confirmed cases locally for more than 50 consecutive days, where did the new coronavirus come from? Why does the outbreak point to the wholesale market? The reporter interviewed Wu Zunyou, chief epidemiologist at the China Center for Disease Control and Prevention.: This new crown outbreak in Beijing, why does the outbreak point to the wholesale market?
: Our researchers typically store biological samples with viruses at low temperatures every day. The lower the temperature, the longer the virus will survive. In wholesale markets, where many sea products are frozen and stored, the virus can survive for a long time and is more likely to infect people. In addition, the wholesale market for agricultural products every day a large number of people in and out, as long as a person carrying the virus, if not found and enter the market, may cause the spread of the epidemic.
based on past knowledge and experience, there are two possibilities for a sudden outbreak of a new local crown in Beijing. The first possibility is that sea products or meat contaminated with the new coronavirus in the wholesale market are the source. Wholesale market a lot of sea products, beef and mutton, etc. are not Beijing's local, but imported from abroad, including overseas imports. There are currently hundreds of thousands of new crown cases worldwide every day, and new crown virus infections can cause contamination when dealing with products or beef and mutton. After these products are shipped to the wholesale market in Beijing, the people in the wholesale market will come into contact with the products when they are in operation. We know that the transmission of the new coronavirus is mainly the spread of droplets and contact transmission. Their hands come into contact with contaminated products, rub their noses and rub their eyes, and they become infected. Symptoms are mild at first, and if you don't realize it, it can also cause human transmission at work. The second possibility is that there are other sources of infection. The wholesale market in Xinfa is very large, the people in the market come from all sides, and the people who enter and leave xinfa wholesale market are the source of infection. For example, he may be a person from other sources, after being infected with very mild symptoms, he did not pay attention to the time, and then caused pollution to the wholesale market in the new origin, resulting in the outbreak of the cluster. Since several of the cases found so far are linked to the wholesale market in the new place, attention has been turned to the new place. Both may exist as to whether contaminated sea products or meat in the market were the initial source of infection, or whether people entering and leaving the market are the source of the infection. But as things stand in Beijing, the first is more likely.
, we need to collect data on the following areas. First, after collecting information on all infected persons and close contacts, the contact relationship between people, the chain of communication and the network of transmission are constructed, which is an epidemiological investigation. The second is to rely on big data technology to sort out the trajectory of all infected people, and their trajectory can give us some hints as to whether they have common exposure points, such as several confirmed patients who have been seen somewhere near the new site in the past few days. Third, laboratory biotechnology, by studying the genetic sequence of the virus to help determine the possible source of the virus. The virus genes of the samples taken were studied and analyzed to see if it was the same as the new coronavirus that appeared in Beijing two months ago, or more similar to Harbin and Shulan, or closer to the virus strains that were prevalent in the United States, Europe and other places. These analyses can provide us with more information. In short, the combination of these three ways, can have a clearer understanding of the new outbreak in Beijing. It is still in the process of gathering information, and there is no way to draw a definitive conclusion.: What is the source of infection in the wholesale market? Is it people flow or logistics? Is it meat fish, or what? Can you do a analysis from the perspective of epidemiological investigation?
: It's hard to tell what the source of infection in the wholesale market is. For example, we can't conclude that salmon is the source of infection because a new coronavirus has been detected in the cutting board of imported salmon. Access to the case board of the owner or items are possible. For example, it is possible that the owner of the case board is a new coronavirus infection, he dropped droplets on the case board during the speech; for example, the guest who may come to purchase the case board is a new coronavirus infection, he stayed in front of the case board for a longer period of time, in the process of communicating with the master or cutting the price of the speech, may also cause the case board to be contaminated; Samples need to be collected through different channels to verify which one is more likely to be evaluated. The wholesale market in Xinfa is full of people, selling too many varieties of goods too complex, not in a short time can be clearly justified. It is only when all the flow and items are clearly checked that it is possible to show the full picture.
the new outbreak, Beijing has been more than 50 consecutive days without locally confirmed cases, it is reasonable to say that there should be no virus. If epidemiological investigations and big data analysis confirm that none of the newly detected new crown confirmed cases or nucleic acid positives have a history of going out, and that they are actually infected in Beijing, then it is possible that imported or contaminated items outside Beijing have brought the virus in. Therefore, we must carefully comb the source channels of new origin items.: Some analysts say that seafood is unlikely to be a source of infection because fish, as low-class organisms, fish virus transmission to humans has rarely occurred, meaning that salmon itself is very unlikely to act as a carrier of the virus. What do you think of this?
: This kind of analysis has some truth, but it is not all right. Wildlife carrying and imported goods carrying are two different concepts. Wild animals such as beavers and bats can carry coronavirus themselves, and the virus breeds in their bodies, but they do not become ill. Imported goods carrying refers to workers infected with the new crown virus in the handling of goods contaminated with these items, contaminated goods imported into the country, others in the process of infection. So wild animals are carrying viruses, and sea products are contaminated after the surface carries the virus. Normal natural fish do not have coronaviruses in their bodies. But after the fish are caught, the treatment workers infected with the new crown virus, which may lead to the fish's surface pollution, and contaminated sea products are shipped to China, Chinese workers in the process of treatment was infected, which in turn led to further human-to-human transmission. Of course, this is only a guess and needs further confirmation from epidemiological investigations.
situation, it is necessary to do a good job of inspection and quarantine of fresh, fruit and vegetables and other goods. Of particular note are two situations: one is an overseas import. At present, the overseas epidemic is more serious than china's, from the outbreak of serious countries to import goods to pay special attention. The other is frozen goods, including sea products, beef and mutton, etc. In these cases, quarantine needs to be strengthened.: Now it is critical to pass our flow, traceability, detection, troubleshooting, so that preventable and controllable, how to do this?
Wu Zunyou: The outbreak occurred early in our country, when the experience of fighting the epidemic is also very small, we were able to successfully control the outbreak, because we resolutely and thoroughly put the control of respiratory infectious diseases 100 percent in place. At that time, China's most serious outbreak, provinces and cities, including Beijing, have been able to successfully control the outbreak, did not cause a wider spread of the epidemic. Now, with a few more sporadic cases, we are confident that we can deal with the outbreak in a timely manner without causing wider spread. Harbin and Shulan are like this, and so is Beijing. We are confident.
different people may understand the four words "preventable and controllable". "Preventable and controllable" is not to say that a case does not appear, but that even if there is a case, we can first find, the first time to deal with, so that the outbreak is controlled to the smallest extent, this is what we call "preventable and controllable." The new coronavirus is a new infectious disease, it is so contagious, patients in the symptoms a few days after the real infection, when they are diagnosed in the hospital, often has caused a certain range of transmission and spread, so it is extremely difficult to control. Therefore, "preventable and controllable" does not mean zero cases zero transmission zero deaths, we must also have a clear, rational understanding of these four words.: In the current situation, what is the risk of spreading the virus?
: Responding to the new crown outbreak is like fighting a war, every minute is extremely precious. Take control of the virus before it spreads, and you take the initiative. In the case of provinces and cities outside Hubei, why hasn't there been a situation like that in Europe before? The key is, from Hubei people back to the local, we first mastered their situation, active contact, the vast majority of them, before they have symptoms have been isolated for medical observation, once symptoms immediately for treatment, did not let them stay in the community too much, did not wait until they became ill and then go to the hospital, did not make these people infected from Hubei have time to cause the spread of the epidemic in the local, this is to seize time.
, as soon as possible to determine the source of infection, check close contacts, avoid secondary transmission, is the focus of the current, Beijing's response speed has been very fast. Several sporadic cases can be analyzed in such a short period of time to lock in the wholesale market of new places. The experience of prevention and control over the past few months, especially the use of technology such as big data, has enabled us to quickly point the way. After determining the direction, the people and environment are then tested, and more direct information is quickly obtained. This important information is not only of great significance to the prevention and control of the epidemic in Beijing, but also may provide new and valuable information to solve the mystery of the spread of the new crown epidemic. I have full confidence in the prevention and control of the outbreak in Beijing. Of course, the next task remains daunting and needs to be continued. The population of close contacts is still large, and a slight omission can create a risk of spreading. So a large number of people have to be involved in the search for close contacts. At the same time, the laboratory should carry out testing and analysis as soon as possible to provide more decision-making basis for epidemic prevention and control.
from the current known information, the Beijing outbreak rebounded, mainly concentrated around the new market. The extension of nucleic acid testing to these areas is more accurate among employees and family members working in the new area, close contacts, and medical staff attending hospitals, and patients attending hospitals at the same time. At present, the scope of the virus has not spread throughout Beijing, the city's more than 20 million people are threatened.
: In the current situation of epidemic prevention and control, beijing residents need to pay special attention to what?
: There is no need to panic, after all, we have accumulated rich experience in epidemic prevention and control, patient treatment and so on. At present, Beijing has taken a series of measures, including the publication of the activity trajectory of confirmed cases, defining the response level in some areas. By defining this information precisely, one can see whether you have been to these places in the past week or two. People who have been to observe their physical condition to see if there are abnormalities, not assured that they can actively apply for nucleic acid testing. For other members of the public, basic hygiene habits such as wearing masks and washing their hands are still to be maintained in places with poor ventilation.