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Original caption: Did the outbreak in the South China seafood market originate from imported seafood? Expert: The possibility of a cold chain being introduced is not ruled out, but there is insufficient evidence to support it
The traceability of the new corona virus has always attracted the attention of the scientific community at home and abroad. Some studies believe that the South China seafood market in Wuhan is not the origin of the virus. Recently, with Qingdao separating the new live coronavirus from the outer packaging of cold chain food for the first time and a document on the possibility that the new outbreak in Beijing could be caused by contamination of food by the cold chain , seems to have proposed another possibility for the traceability of the virus. Wu Zunyou, chief epidemiology expert at the Chinese Center for Disease Control and Prevention, said in a recent media interview: “Because the outbreaks in Beijing Xinfadi, Dalian and Qingdao were caused by shellfish, we recalled the first outbreak in Wuhan. Those epidemics are also in the South China seafood market. Are they also caused by imported seafood? This also gives us a clue, giving us a new idea and a new technological direction. “
According to the news published by the Chinese Center for Disease Control and Prevention on the 17th, during the traceability investigation of the Qingdao epidemic, the Chinese Center for Disease Control and Prevention detected and isolated the new coronavirus from packaging exterior of imported frozen cod worn by workers. This is the first time in the world for cold chain food. The new live coronavirus was isolated in the outer packaging and it was confirmed for the first time that the new coronavirus can survive in the outer packaging of items for a long time under the special conditions of cold chain transport, which shows that the new coronavirus it uses elements of the cold chain as transporters and has long-distance cross-border import. It is possible, and under certain environmental conditions, that the virus on the surface of the article can cause infection of susceptible contacts without effective protection. On the morning of the 20th, at a press conference held by the Qingdao municipal government, Qingdao Deputy Mayor Luan Xin said that a complete chain of evidence has been found in the Qingdao epidemic prevention and control work, indicating that the new corona virus can be transmitted from person to person and can be transmitted in freezing conditions. Long-term survival.
Gao Fu, director of the Chinese Center for Disease Control and Prevention, said: “In the past, samples were ‘detected’ positive for coronavirus nucleic acid. Positive nucleic acid is not necessarily a live virus. This time , the live virus ‘isolated’ means that there must be a live virus and it can cause Spread or infected. ”It is worth mentioning that as the“ patient zero ”of the Qingdao epidemic, Dong and Chen loaded and unloaded workers in Qingdao Dagang. They loaded and unloaded frozen seafood imported from abroad on the night shift on September 19.
On the 23rd, researchers from Tsinghua University, the Beijing Center for Disease Control and Prevention, the Institute of Pathogenic Biology, the Chinese Academy of Medical Sciences, Peking University and the Chinese Academy of Genomics Institute of Sciences of Beijing published an online publication titled “New Coronary Pneumonia of Beijing” in the magazine “National Science Review”. The recurrence of the epidemic may have its origin in research work on food contamination in the cold chain. Based on nucleic acid sequencing and virus genome sequence analysis of samples related to the Beijing epidemic in June 2020, environment and food, combined with comprehensive epidemiological investigation and big data analysis, the document revealed that the epidemic may be caused by food contamination from the cold chain. It is proposed that cold chain transport may be a new way of spreading the new coronavirus.
Not just in Qingdao and Beijing, but in the Dalian outbreak in July, most of the confirmed cases in the previous days were employees and family members of Kaiyang Seafood Company. Although no live virus was isolated from the aquatic products of the cold chain, it could not be formed. A complete chain of infection, but there is still the possibility of the virus spreading through cold chain transport.
Some experts in related fields have noted that items transported under the cold chain, especially imported seafood, can spread the new corona virus, which may suggest a new research direction for traceability of the virus in the Wuhan seafood market. in southern China. As the largest aquatic products wholesale market in central China, the South China seafood market has a large number of imported products transported through the cold chain. Yang Zhanqiu, professor at the Institute of Virology, Faculty of Basic Medicine, Wuhan University School of Medicine, told the Global Times reporter on the 28th that if there was a transaction of imported seafood in the South China seafood market , it is possible that the new coronavirus is imported through cold chain transport.
Reporters from “Global Times” reviewed public reports and found that there were many stores selling fresh imported food in the South China seafood market, selling seafood such as king crabs and Arctic shellfish, as well as meat products from Brazil and Germany that they needed cold chain transport.
Wu Guizhen, chief biosafety expert at the China Centers for Disease Control and Prevention, also mentioned in a recent media interview: “In the past, we were looking for intermediate hosts when tracing the virus. it may be time to re-examine whether the virus comes from wild animals. ” Wu Guizhen said: “The epidemic recovered in Beijing and also concentrated on the wholesale market. However, unlike the South China seafood market in Wuhan, the possibility of wild animals in Beijing causing the epidemic is very This leaves us with a very important reminder: is it true? But Energy Head is an infected person or a contaminated food, and the seafood market environment creates an opportunity for rapid spread. “
However, the relevant conjectures still lack sufficient evidence to support the formation of a clear chain of infection. Yang Zhanqiu mentioned that if the source is blocked in imported products from the cold chain transportation, it is necessary to answer the core questions of how the product is contaminated by the virus and where is the source. One possibility is that foreign personnel involved in cold chain transportation have become infected with the new coronavirus and spread the virus to shellfish and other products while working. Another possibility is that imported animal products themselves are infected with the new coronavirus. “Previously, the focus of traceability of the virus was on wild animals, such as bats, but it did not focus on the possibility of fish, pigs, cows, sheep, etc. spreading the new corona virus,” Yang said Zhanqiu. Based on prior knowledge of coronaviruses, these animals were infected. The virus does not infect people, but the new coronavirus can overturn these conclusions. “However, none of the speculations above is supported by sufficient evidence.”
An anonymous virology expert also told a “Global Times” reporter on the 28th that cold chain transmission remains a secondary pathway for the spread of the new corona virus, and that the possibility of this method infect such a large population in Wuhan is not high. Also, if the virus is imported from abroad, it is also necessary to explain why the source of the virus did not have the first outbreak. Some analyzes also pointed out that some patients who appeared in Wuhan in the earlier period had no history of contact with the South China seafood market. These issues have yet to be studied. (Zhao Juehui)
