Professor Tong Yigang, a domestic virus traceability expert and dean of the School of Life Sciences and Technology of Beijing University of Chemical Technology, said in an exclusive interview with CGTN host Liu Xin that it is likely that the early infected people are not in Wuhan, not in Hubei, not in China, and the traceability report issued by the US intelligence agency is also too politicized. Why doesn't the "laboratory leak theory" hold? Is the virus traceability still advancing? What is the status of cooperation between the China-WHO Joint Expert Group? The following is a transcript of the interview.
Intermediate host transmission – the most likely route of transmission of the new crown virus
Liu Xin: You are the Chinese team leader of the Animal and Environmental Studies Group of the China-WHO Joint Expert Group on Covid-19 Traceability, and in the Joint China-WHO Report released in March 2021, you pointed out that the new crown virus is "comparative or very likely" to be introduced into humans through intermediate hosts. Where is its basis? Which animals are likely to be such intermediate hosts?
Tong Yigang: Hello, thank you for this question. On this issue, we have repeatedly communicated with WHO experts, we have made some comparisons of different possibilities, and the most likely way to get transmission may be through the intermediate host, which is a result after comparing the positive evidence with the negative evidence.
Bat sampling in a laboratory in Ratchaburi Province, Thailand, September 12, 2020. /Visual China
According to the current research results, bats are likely to be its natural hosts, because we have now found a lot of bats, not only Bats in China, Bats in Southeast Asia, bats in many countries with similar viruses, so bats are the most likely natural hosts. Then bats, as an animal that does not have much contact with humans, are relatively less likely to spread directly, so we think that it is more likely to spread through an intermediate host, so far we have not found much intermediate host.
But so far we have found several animals that can spread the new crown virus, one is the pangolin, which carries a virus that is closer to the new crown virus, but the virus found in the pangolin and the new crown virus are still very large, so there is no evidence that the new crown virus is derived from pangolins. Then some other animals, including cats and dogs, proved to be infected with the new crown virus at an early stage.
Recently found in the United States, the white-tailed deer can also be infected with the new crown virus in large quantities. Because antibodies to the virus were also found in some specimens in 2019, this phenomenon indicates that it is possible that the new crown virus is already in the white-tailed deer in 2019, which is also valuable for our traceability research. So we feel that it is necessary to further understand the genome sequence of the virus carried by the white-tailed deer, through the comparison of the genome sequence, we can see whether the virus carried by the white-tailed deer is early or late, and what kind of relationship with the origin of the new crown virus, (this) is more helpful for our future research on the origin of the new crown virus.
So by the way, there is also a recent development, that is, the new crown virus has been carried by patients with skin diseases in Italy. Some of these early samples were collected in August and September 2019, which is three months earlier than the earliest infected patients found in Wuhan, and this evidence is still relatively conclusive, because it is not only found in the patient's blood, but also in the urine, and the antibody is detected in its serum, that is, it found both the sequence of its nucleic acids and the evidence of antibodies, so this result is relatively credible.
On June 9, 2021, the National Institute of Oncology in Milan issued a press release that the new crown virus may have spread in Italy in 2019. National Institute of Oncology, Milan, Italy, June 17, 2021. /Visual China
Liu Xin: Following on what you just said, I would like to ask you about the fact that there are these reports in Europe. Do you think that the hypothesis that the coronavirus enters the human body through an intermediate host also applies to these examples in Europe?
Tong Yigang: In fact, there is no contradiction. The latest evidence in Europe and Italy, it only proves that these people were infected at an early stage, so it is difficult to determine what kind of infection he himself is, it is impossible to determine. But this matter can give us a hint, perhaps through the study of these patients, we can find some early infected people, some of his occupational characteristics or one of his exposure histories, to find possible animal sources through some of these evidences. Then this virus must be derived from animals, as for what kind of animals, through the intermediate host or directly from the natural host, we need to further study.
Second, what is the current progress of virus traceability?
Liu Xin: In March 2020, together with nearly 30 other scientists, you published a paper in nature entitled "Identifying SARS-CoV-2-related coronaviruses in Malayan pangolin", which reported malay pangolins seized during anti-smuggling operations in southern China. They carry coronaviruses that are very similar to SARS-CoV-2. What direction do you think such a paper provides for traceability work?
Tong Yigang: This incident was actually a very early thing, that is, as early as the end of 17 and the beginning of 18, we received some samples of pangolins who died of illness of unknown causes, and these samples were taken in an animal rescue station. The purpose of these rescue stations is to raise and rescue some protected animals that have been smuggled and intercepted, but in the process of rescue, the animals have disease and death, and in the case of unknown reasons, they send us samples for analysis. In the course of our analysis, we found that one of the coronaviruses was mainly derived from Southeast Asian animals, because the number of pangolins in China is very small, and the pangolins found are all Malay pangolins, not native to China.
After we analyzed the virus, we didn't pay much attention to it, thinking it was a new coronavirus, and we didn't know how much it meant. In fact, it was not confirmed that this coronavirus was the cause of the death of pangolins, because not only the coronavirus was found in these specimens, but also some other viruses, such as canine parvovirus.
Then after the outbreak of the new crown epidemic, the sequence of the new crown virus was announced. We found through comparison that the original pangolin carries a high homology to the coronavirus and the new crown virus, of course, it is relatively high compared to some other viruses, but it is compared with the virus carried by bats, its homology is not as high as the homology of bats.
Tong Yigang, Dean of the School of Life Sciences of Beijing University of Chemical Technology and head of the Animal and Environmental Studies Group of the China-WORLD World Health Organization Joint Research Expert Group on The Traceability of the New Coronavirus, attended the press conference and answered reporters' questions, March 31, 2021. /Visual China
But also from another perspective, we can guess that the pangolin coronavirus, it may be and the new crown virus to some extent, in the process of evolution, there are some common ancestors, there are some evolutionary interactions, for example, there may be a problem of recombination of the middle local area. This was a relatively important discovery at the time, because no more coronaviruses were found at that time, so we found that this virus was actually a very early, except for bats, which was closer to the new coronavirus.
So this meaning is that it may have some hints for us to understand the source of the new crown virus, but in fact it does not prove that the new crown virus is derived from pangolins, because it is still very different from the virus carried by pangolins.
Third, fully support the traceability work, but China should never be a "wronged head"
Liu Xin: In March this year, you said at a press conference that from 2018 to 2020, 31 provinces, municipalities and autonomous regions in China collected more than 38,000 samples of livestock and poultry and more than 41,000 samples of wild animals. By testing these samples, the Chinese authorities have not found any samples that have tested positive for the new crown virus, what does this mean? Will our follow-up research cover more animal species susceptible to COVID-19?
Chinese Center for Disease Control and Prevention, Beijing, China, September 1, 2020. /Visual China
Tong Yigang: After the outbreak of the new crown epidemic, our country and our domestic scientists have attached great importance to the source of the new crown virus. Because this epidemic was first discovered in China, we initially suspected that the virus should be somewhere in the country, in an animal. Not only do we scientists spontaneously do a lot of research, all those who have the resources and ability are doing research in this area; our national government also attaches great importance to this aspect of work, and also encourages scientists and various government departments to coordinate some samples to carry out this work.
After the new crown epidemic, we made tens of thousands of poultry and tens of thousands of wild animal specimens, unfortunately we did not find any clues, proof that the new crown virus exists in these wild animals and domestic animals, and even the homologous virus that can reach 80% or 70% or 80% of the new crown virus, so we are very skeptical of the original idea. Of course, we can't rule out the source of the virus in China now, because at present, not all animals have been detected, but after so much effort, we feel more and more that the source of this virus is relatively small in China, so as more evidence appears, we feel that this virus may be abroad, because we found that the virus with the highest homology is in bats, and there are a large number of such viruses in bats in Yunnan Province, which borders neighboring countries in southern China. Then these viruses may be in some of the surrounding countries. Some other recent studies have also shown that many neighboring countries do have some viruses that are more homologous to the new crown virus, and even some samples from 10 years ago have the same virus of the new crown in these countries. Recent nucleic acid and antibody positive samples from early patients in Italy also show from one side that it is likely that the early infected people are not in Wuhan, not in Hubei, not in China.
Fourth, scientific guidance, continue to trace the source of the virus
Liu Xin: You just mentioned that because so many domestic samples have not been found positive, now we may think that the earliest source is not in China at all, but on the other hand, you also said, and we have also seen that the virus that is most similar to the new crown virus is called RaTG13, which is actually found in bats in southern China, so are these two findings contradictory?
Tong Yigang: It's not contradictory, but I think they can be corroborated by each other. Because we just said that we have done a lot of work before, and we have not found that any animal in China has a virus that is relatively close to the new crown virus, not to mention the same virus, and there is no virus that is connected to the nearest. In Southeast Asia, there are also many countries that have found viruses that are closer to the source of the new crown virus and have a high homology to the new crown virus, which shows that they are related.
So the bat itself is found in this part of China's Yunnan Province, it and Southeast Asian countries are bordered, and the bat can fly, it can fly a long distance, through such some migratory actions, will make the virus in a relatively wide area to exist, to spread.
So outside of Yunnan, there may be some bat-carried viruses in neighboring countries, which may be the source of the real new crown virus, of course, we still need scientific evidence, this is just an idea, so this idea also needs more research. We also hope that scientists from various countries in the world, under the coordination of WHO or other organizations, can carry out more cooperation to study the origin of this virus and do some research in more animals in more regions.
Researchers capture bats in Khao Chong Pran Cave, Ratchaburi Province, Thailand, September 12, 2020. /Visual China
Liu Xin: Do domestic scientists still have research on possible potential hosts? Is this kind of research still going forward? If so, what kind of research?
Tong Yigang: Of course, this work is not over, because the source of the new crown virus has not been found, and we continue to be interested in this issue. And this problem is also a very important issue, which may have a reference role for future outbreaks, the emergence of new outbreaks, and similar outbreaks, so we still need to clarify the source of the virus.
We are still further tracking the source of the virus, and we are constantly trying to obtain more domesticated, wild animals, artificial animals, and some of these animal specimens. At the same time, we are also further searching for other wild species, including bats, some highly suspicious animals to test, in fact, there are some data continue to appear, and there may be more literature reports in the near future.
Fifth, why is the "laboratory leak theory" absurd to the extreme
Liu Xin: The first phase of the joint traceability report between China and the World Health Organization points out that it is extremely unlikely that the new crown virus will be transmitted through laboratory events, so how did this argument come about? What exactly does it refer to?
Tong Yigang: For this question, I think there may be three reasons that it is extremely unlikely to leak from the laboratory, but these reasons were also fully discussed with WHO experts at that time, and finally came to such a conclusion.
Historically, the leakage of pathogens has caused epidemics many times, but there is a problem here, that is, all these viruses or pathogens that have leaked in history are because someone has cultivated it, someone is studying it, it is a known thing that already exists in the laboratory, so its leakage is improper operation or poor management that has led to an accident.
Peter Ben Ambalek, head of the WHO Expert Group: "The coronavirus has not been deliberately used by laboratories." Geneva, Switzerland, 12 February 2021. /Visual China
But when this outbreak occurred in Wuhan, no laboratory in Wuhan knew about such a virus, and no laboratory was studying such a virus, so this is completely different from any laboratory leak in history, so it is completely unfounded to infer that the new crown epidemic originated from laboratory leakage by such a thing as a laboratory leak in history.
The second reason is the Wuhan Institute of Virology, which is a research institute built in accordance with international standards, one of the most complete and advanced research institutes in China, of course, its management level is also very high, it is completely in accordance with international standards for standardized management. At the level of management, it is also impossible for a leak to occur. The Wuhan Institute of Virology has also trained people from many countries in the world, and I also know some of their external training. So I felt that such a leak could not happen in a strict laboratory like this, and it was a laboratory that specialized in biosafety research.
The third reason is that from the evidence, after the outbreak of the new crown epidemic, the local government department and the Wuhan Virology Institute itself tested the serum saved by all the staff, and also carefully investigated the health of all their staff, and found that in the stage of the outbreak in Wuhan, no one in the Wuhan Virology Institute had a new coronavirus infection. Although there are relatively high people infected in Wuhan, no one in the Wuhan Virus Institute is infected, which is an objective fact, which is well documented. So some people say that Wuhan (the Institute of Viruses) is infected, in fact, they made up the story, there is no evidence to prove that all people in Wuhan virus are infected, in fact, there is no infection, this is well documented.
Comics: Subverting the Truth? /CGTN
I think why many people always talk about laboratory infections, in fact, the problem is that many people prefer to tell stories, because leaking from the laboratory this story sounds very beautiful. But if you want to prove where you came from, you need scientific evidence, and in the absence of scientific evidence, everyone likes to tell stories, and the story is also very attractive, so it leads to the story being widely circulated. But I think we scientists still have to tell the truth, and we need to get evidence of the virus to say this.
At that time, after the investigation of the Wuhan laboratory, it was concluded that the laboratory (leak) was extremely unlikely, and a sentence was added to the end, that is, in the absence of new evidence related to the laboratory, then WHO would no longer carry out this investigation.
Traceability calls for international cooperation rather than political manipulation
Liu Xin: You were also involved in joint research at that time, and in January and February 2021, you and your foreign colleagues in the Animals and environment group, what was the situation of cooperation between you? For example, will there be disagreements or arguments between the two sides? If so, what is the biggest disagreement or controversy? In the end, how did you reach a final agreement to form such a report?
Tong Yigang: In the process of our joint investigation with international experts, both of us are very positive and very friendly, and both sides have cooperated very well. In most cases our views are the same because we are judged on the basis of scientific facts. We will discuss the possibility of each virus spreading, from the positive and negative sides to the evidence to discuss the possibility.
The World Health Organization's International Expert Group on Covid-19 Traceability holds a press conference with Chinese scientists on joint scientific research cooperation on the traceability of the new crown virus, Wuhan, Hubei Province, February 9, 2021. /Visual China
So in many cases the results we get are similar or the same, but sometimes there are some differences in the use of words, and the parties put forward some views on the expression of words, but this does not affect our entire conclusion.
In the whole process, there may be some inconsistencies, for example, there may be some slight differences on the issue of cold chain transportation, but in the end there is still a unified opinion, that the virus is introduced to Wuhan through the cold chain, this possibility exists, it is possible.
Liu Xin: Finally, what do you think of the US intelligence agencies being required to issue a report on the traceability of the new crown virus, and what kind of impact do you think such a practice will have on international joint traceability scientific research?
Comics: "Public Accusations". /CGTN
Tong Yigang: I don't think it is suitable for me to answer this question. We're talking about science, and of course some of that involves some of the exchanges we had with WHO experts in the first phase, and I'm also going to explain it based on my experience, but there are some things that are too politicized, and I don't think I'm good at commenting on that.