Xinhua News Agency, Beijing, March 9. 2021. Since the outbreak of the novel corona pneumonia, the origin, spread and evolution of this virus have attracted much attention. Many domestic and foreign experts said that it is still impossible to confirm where the novel coronavirus originated based on the existing evidence.
Dissemination “puzzle” is missing
How did the spread of the novel coronavirus in humans begin? Judging from the first reported cases and incomplete data, it was originally assumed that the South China Seafood Market in Wuhan was the origin of the epidemic. However, in a paper published in January in the British magazine “The Lancet”, Huang Chaolin, vice president of Wuhan Jinyintan Hospital, (and others) analysed the first batch of 41 confirmed cases of novel corona pneumonia and found that only 27 of those infected had been in direct contact with the South China Seafood Market. This retrospective study concluded that the first confirmed patient became ill on December 1, 2019, but this patient zero had no history of exposure to the South China Seafood Market – with no epidemiological link with later confirmed cases – as his infected family members did not manifest fever or respiratory symptoms.
In a related report on the website of the American “Science” magazine – Christian Anderson – a biologist at the Scripps Research Institute in the United States, speculated that the novel coronavirus may have entered the South China Seafood Market through three scenarios: it may be caused by an infected person, an animal or a group of people – as this is a hub where humans and animals intermingle at a fast rate of exchange, etc. Many experts and studies support the above view – Wilt Ian Lipkin – a professor at the Mailman School of Public Health at Columbia University, known as the “virus hunter”, said that the connection between the novel coronavirus and the South China Seafood Market may not be so direct – forming only a “second transmission” – with the virus having spread to the area from somewhere else.
Researchers from Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences – and other institutions – recently released a paper in the form of an over-view, saying that they analysed the genome data of 93 novel coronavirus samples from 12 countries on four continents and found that they contained 58 haplotypes, which are similar to the South China Seafood Market. The haplotypes of the related patient samples are all H1 or its derived types, while the “older” haplotypes such as H3, H13, and H38 come from outside the South China Seafood Market, confirming that the novel coronavirus in the South China Seafood Market did not originate there and was transmitted from other places. To uncover the chain of transmission of the novel coronavirus, scientists still lack some “puzzle-pieces”, among which the most critical piece is the first infected person, often referred to as “patient zero”. “Patient Zero” is the confluence of many questions, which is crucial for finding intermediate hosts and answering questions about how the virus is transmitted from animals to humans.
A well-known example is the “Spanish flu” that was estimated to have killed tens of millions of people around the world a hundred years ago. Although this epidemic was named after the first report in Spain, some retrospective studies later found that the first infected person may be from the United States. A soldier in the Kansas State Barracks. Daniel Lucy, an infectious disease expert at Georgetown University in the United States, said that considering factors such as the incubation period of the virus, the first person infected with the novel coronavirus may have appeared in November 2019, or earlier. From the perspective of the global spread of the novel coronavirus, although most cases can be traced to the source of infection, countries such as the United States have reported many cases that cannot be traced. In Italy, where the epidemic is getting worse, the domestic “patient zero” has not yet been found.
Virus traceability is not complete
The novel coronavirus originated from animals. How did it survive and evolve in nature before it entered the human body? Researchers from the Wuhan Institute of Virology of the Chinese Academy of Sciences (and other institutions) published a paper in the British journal Nature in February, saying that they found that the novel coronavirus is 96% identical to coronavirus (TG13) found in bats. TG13 is the most similar virus strain known in relation to the novel coronavirus, indicating that bats are likely to be the natural host of the novel coronavirus. Other studies have also found that the novel coronavirus is similar to the coronavirus gene sequence carried by pangolins, especially in the receptor binding domain that allows the virus to enter the cell. This indicates that during the evolution of the new coronavirus, TG13 may have recombined with the coronavirus carried by the pangolin. Although relevant research has provided clues, many experts interviewed by Xinhua News Agency reporters said that the origin and intermediate host of the novel coronavirus are still difficult to determine, and it may take longer to trace the virus to its source.
Jonathan Ball, a professor of molecular virology at the University of Nottingham in the UK, said that the link between the human novel coronavirus and the pangolin is still a “small question mark”, and there is still no final answer as to the source of the virus. But if you put all the individual clues together, they point to an event in which a virus spread from animals. Charlie Calischer, a professor in the College of Veterinary and Biomedical Sciences at Colorado State University in the United States, said that he is open to discussing the source of the novel coronavirus, but that conclusions require scientific data in support – and not speculation. Stanley Perlman, a professor of microbiology and immunology at the University of Iowa in the United States, believes that the animals that serve as the intermediate host of the novel coronavirus may come from outside China, such as smuggled pangolins and other animals.
The “China-World Health Organization Novel Coronavirus Pneumonia (COVID-19) Joint Investigation Report” released at the end of February also pointed out that the “limitations of existing knowledge” include “animal source and natural host of the virus” and “animals in the initial stage”. Human infection process” “early exposure to cases with unknown history” and so on. The global epidemic is still spreading, and many questions remain to be answered by scientific researchers from all over the world. As WHO Director-General – Tedros Adhanom Ghebreyesus – has repeatedly emphasized, in the global fight against the novel corona pneumonia epidemic, “facts are needed, not fear”, “science, not rumours”, “unity, not stigma” are needed. [Participating reporters: Zhang Ying (张莹), Zhou Zhou (周舟), Zhang Jiawei(张家伟)]
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