Why is it difficult to trace the new coronavirus?

　　(Fighting against New Coronary Pneumonia) Why is it difficult to trace the source of New Coronavirus?

　　China News Service, Beijing, May 20 (Li Jingze) The new crest virus is ferocious, and its wide range shows its "ambition" to blame humanity. Out of the urgency of scientific prevention and control, the exploration of unknown things, the virus traceability has continued attention.

　　Previously, researchers from all over the world have analyzed the new coronavirus genome and published the results publicly, proving that the virus originated from wild animals. This means that it is likely to spread from the natural host across species to the intermediate host, and then from the intermediate host to the human. And this seemingly simple chain of communication is full of mist, hindering the pace of scientists' exploration.

　　Early studies have shown that the sequence of the new coronavirus is highly similar to the two coronavirus sequences that naturally parasitize bats, proving that the natural host of the new coronavirus is probably bat, but the intermediate host from bat to human remains mysterious.

　　A study published online in the journal Nature found that pangolins may be potential intermediate hosts for new coronaviruses based on genomic data comparison analysis. But the researchers said that, given that this is a retrospective study, the specific virus source of the outbreak has yet to be determined.

　　Cao Wuchun, a researcher at the Institute of Microbiology and Epidemiology, Institute of Military Medical Sciences, Academy of Military Sciences, said in an interview with the China News Service that the new coronavirus has a high rate of transmission from person to person, suggesting that the virus may have evolved in the intermediate host. It is very different from the previous virus transmission to people.

　　Researchers at the University of London Institute of Genetics published a paper entitled "Genomic Diversity of SARS-CoV-2 and the emergence of recurrent mutations" which also confirmed the virus's ability to evolve. From May to December 11, 2019, it may have spread rapidly around the world and is still undergoing repeated mutations to adapt to its human host.

　　"A change in the nature of the virus means changes in conditions and propagation paths. Scientists can't follow the original traceability script, but must constantly explore new methods." Cao Wuchun told reporters.

　　Looking at the "patient zero" as an intermediate host to the human node, it has been a mystery so far.

　　The academic term corresponding to "Patient Zero" is "primary case", which can be understood as the virus entering the human body for the first time in this case. The animal may infect one person or a group of people.

　　According to an article published in the authoritative medical journal "The Lancet" by Huang Zhaolin, deputy director of Wuhan Jinyintan Hospital, and others, as the earliest country to report the outbreak, the first case in China was on December 1, 2019. Considering the incubation period, the patient should be infected with the virus in November 2019.

　　But the first reported cases are not necessarily the source of the virus. With the development of virus tracing work in various countries, the timeline for tracing "patient No. 0" in many countries is gradually advancing. By comparison, it is difficult to reach a consensus.

　　An article in the medical journal International Journal of Antibacterial Agents entitled "New Coronavirus has been circulating in France at the end of December 2019" shows that a person infected with influenza between December 2, 2019 and January 16, 2020 In severe cases, the nucleic acid test was positive. The case is not related to China, and there was no history of foreign travel before the onset, indicating that the new coronavirus has spread in France at the end of December 2019.

　　Giuseppe Remuz, director of the Mario-Negri Institute of Pharmacology in Milan, Italy, found that in late November and December last year, more than 10 cases of clinical suspicion unrelated to seasonal influenza occurred in Crema and other regions In cases of new pneumonia, this may mean that the new coronavirus has been lurking in Italy for several months without detection.

　　The above research shows that before the confirmed cases were found in China, other countries had similar confirmed cases. Where is "Patient Zero"? The world's scientists are still difficult to give the answer.

　　Jin Qi, director of the Institute of Pathogenic Biology of the Chinese Academy of Medical Sciences, said that seroepidemiology is a way to find "patient zero", and there are indeed seropositive backgrounds in the current population, but it is difficult to clarify the infection due to the lack of relevant records time. In addition, the asymptomatic infected persons in this new coronary pneumonia epidemic have added mist to the source of the virus. Jin Qi said that if the "patient No. 0" is an asymptomatic or mildly symptomatic infected person and has no medical records, there is no way to identify him Up.

　　For scientific researchers, the difficulty of tracing the source is truly reflected in the intersection of the complicated data and multi-disciplines in the research process. Jin Qi said that traceability requires interweaving clues from computational biology, bioinformatics, epidemiology and other disciplines into a network that confirms each other.

　　It is even more difficult to achieve mutual verification. To date, AIDS, Ebola, SARS and other epidemics have never clearly found a "zero patient" in the strict sense, and the chain of transmission of some viruses from natural hosts to humans has not been completely confirmed.

　　"We cannot give up searching because of difficulties." Cao Wuchun believes that the purpose of tracing the source is to make the current prevention and control find the target. In the long run, it is to avoid the similar epidemic situation from causing harm to human society.

　　Similarly, we cannot ignore science and subjective conjecture because of difficulties. World Health Organization spokesperson Fadra Shaib said that professional questions such as "the origin of the virus" should be left to scientists and public health experts to answer. Scientific questions should be revealed by scientists. It has gradually become the consensus of the international community. Teams in many countries, including China, are cooperating on the issue of virus tracing. (Finish)