Is the outbreak in the South China seafood market originated from imported seafood?

Expert: The possibility of cold chain introduction is not ruled out, but there is insufficient evidence to support it

　　[Global Times reporter Zhao Juehui] The traceability of the new coronavirus 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 for the first time separating the live new coronavirus from the outer packaging of cold-chain food and a paper on the possibility that the new outbreak in Beijing may be caused by cold-chain food contamination, it seems to have proposed another possibility for virus traceability.

Wu Zunyou, chief epidemiologist of the Chinese Center for Disease Control and Prevention, said in a recent interview with the media, “Because the outbreaks in Beijing Xinfadi, Dalian and Qingdao were all caused by seafood, it reminded us of the earliest outbreak in Wuhan. Those epidemics are also in the South China Seafood Market. Is it also caused by imported seafood? This also gives us a hint, allowing us to have a new idea and a new technological direction."

　　According to the news released 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 the outer packaging of imported frozen cod carried by workers. This is the first time in the world for cold chain food. The live new coronavirus was isolated on the outer packaging, and it was confirmed for the first time that the new coronavirus can survive on the outer packaging of items for a long time under the special conditions of cold chain transportation, which indicates that the new coronavirus uses cold chain items as carriers and has long-distance cross-border import It is possible, and under certain environmental conditions, that the virus on the surface of the article may cause infection of susceptible contacts without effective protection.

On the morning of the 20th, at a press conference held by the Qingdao Municipal Government, Luan Xin, deputy mayor of Qingdao, said that a complete chain of evidence has been found in Qingdao’s epidemic prevention and control work, indicating that the new crown virus can be transmitted from person to person and in freezing conditions. Under long-term survival.

　　Gao Fu, director of the Chinese Center for Disease Control and Prevention, said, “In the past, samples were'detected' positive for the nucleic acid of the coronavirus, which is not necessarily a live virus. The'isolated' live virus means that there must be a live virus and can cause Spread or infection.” It is worth mentioning that as the “patient zero” of the Qingdao epidemic, Dong and Chen were loading and unloading 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, Beijing Center for Disease Control and Prevention, Institute of Pathogenic Biology, Chinese Academy of Medical Sciences, Peking University, and Beijing Institute of Genomics, Chinese Academy of Sciences published an online publication titled “Beijing New Coronary Pneumonia” in the journal “National Science Review”. The recurrence of the epidemic may originate from the research paper on food contamination in the cold chain.

Through the nucleic acid sequencing and viral genome sequence analysis of samples related to the Beijing epidemic in June 2020, the environment and food, combined with a comprehensive epidemiological investigation and big data analysis, the paper revealed that the epidemic may be caused by cold chain food contamination. It is proposed that cold chain transportation may be a new way for the spread of the new coronavirus.

　　Not only Qingdao and Beijing, but in the outbreak in Dalian in July, most of the confirmed cases in the previous few days were employees and family members of Kaiyang Seafood Company. Although no live virus was isolated from cold chain aquatic products, it could not be formed. A complete infection chain, but the possibility of the virus spreading through cold chain transportation still exists.

　　Some experts in related fields have noticed that items transported under the cold chain, especially imported seafood, can spread the new crown virus. This may suggest a new research direction for virus traceability in Wuhan South China Seafood Market.

As the largest aquatic product wholesale market in Central China, the South China Seafood Market has a large number of imported products transported through the cold chain.

Yang Zhanqiu, a professor at the Institute of Virology, School 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 for the new coronavirus to be imported through cold chain transportation.

　　"Global Times" reporters checked public reports and found that there were many shops selling imported fresh 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 needed cold chain transportation.

　　Wu Guizhen, chief biosecurity expert of the China Centers for Disease Control and Prevention, also mentioned in a recent interview with the media, “In the past, we have been looking for intermediate hosts when doing virus traceability. Now it may be time to re-examine whether the virus comes from wild animals.” Wu Guizhen said, “The epidemic rebounded in Beijing, and it was also concentrated in the wholesale market. However, unlike the South China Seafood Market in Wuhan, the possibility of wild animals in Beijing causing the epidemic is very small. This leaves us with a very important reminder: Is it true? But energy head is an infected person or contaminated food, and the environment of the seafood market creates an opportunity for rapid spread."

　　However, relevant conjectures still lack sufficient evidence to support the formation of a clear chain of infection.

Yang Zhanqiu mentioned that if the source is locked in the imported products of 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 been infected with the new coronavirus and spread the virus to seafood and other products while working.

Another possibility is that the imported animal products themselves are infected with the new coronavirus.

"Previously, the focus of virus traceability was on wild animals, such as bats, but it did not focus on the possibility of fish, pigs, cattle, sheep, etc. that spread the new coronavirus." Yang Zhanqiu said, according to past knowledge of coronaviruses, these animals have been infected. The virus does not infect people, but the new coronavirus may overturn these conclusions.

"However, none of the above speculations is currently supported by sufficient evidence."

　　An unnamed virology expert also told a "Global Times" reporter on the 28th that cold chain transmission is currently still a secondary way for the spread of the new crown virus, and the possibility of this method infecting such a large population in Wuhan is not high.

In addition, if the virus is imported from overseas, why the source of the virus did not have the first outbreak is also a question that needs to be explained.

Some analysis also pointed out that some patients who appeared in Wuhan in the earliest period did not have a history of contact with the South China Seafood Market, and these issues still need to be studied.