Since the onset of new coronavirus pneumonia, much attention has been paid to the origin, spread and development of the new virus. Many experts argue that, based on the available data, it is still impossible to accurately determine where the new type of virus came from.
How did the transmission of the new virus from animals to humans begin?
From the initially recorded cases, the outbreak was believed to have been the South China seafood market in Wuhan.
However, in January, Huang Chaolin, deputy director of one of the hospitals in Wuhan and other specialists, after analyzing the first 41 cases of diagnosed coronavirus pneumonia, found that only 27 of those infected had visited the South Chinese seafood market. According to the results of the study, the first confirmed case of the disease occurred on December 1, 2019, while the victim had no contact with the seafood market in South China and there was no epidemiological connection with subsequently confirmed cases, and his family did not experience fever and respiratory symptoms.
In a related report on the website of the American journal Science, Christian Anderson, a biologist at Scripps Research Institute in the USA, suggested that there could be three scenarios for a new coronavirus to appear in the South China seafood market: it could be an infected person, animal, or group of people.
Many experts and studies support this view. Wilt Jan Lipkin, Professor, School of Public Health Melman at Columbia University, known as the “virus hunter,” said that the link between the new coronavirus and the South China seafood market may not be as direct, and perhaps what happened on the market was a “secondary transmission,” but the virus began to mutate and spread earlier.
Researchers from the Chinese Academy of Sciences recently published a document saying that they analyzed the genomic data of 93 samples of the new coronavirus from 12 countries on four continents and found that they contained 58 haplotypes that are associated with the seafood market in South China. The haplotypes of the associated patient samples were H1 or its derivatives, while the “older” haplotypes, such as H3, H13, and H38, came from outside the South China seafood market, which confirms that the new coronavirus in the South China market seafood got there from another place.
To restore the transmission chain of the new coronavirus, scientists still lack some components, the most critical of which is the first infected person, who is also called the “zero patient”. A “null patient” is the answer to many questions that are crucial to finding intermediate hosts and answering questions about how the virus is transmitted from animals to humans.
A notable example is Spanish flu, which is estimated to have killed tens of millions of people around the world a century ago. Although the epidemic was named after the first case in Spain, some retrospective studies later found that the first infected person could come from the United States.
Daniel Lucy, an infectious disease expert at Georgetown University in the United States, said that, given factors such as the incubation period of the virus, the first case could have appeared in November 2019 or earlier.
Judging by the global spread of the new coronavirus, although most cases can be traced to the source of infection, countries such as the United States report many unexplored cases. In Italy, where the epidemic is worsening, the “null patient” has not yet been established.
Tracking the spread of the virus is not complete
It is established that the new coronavirus originated from animals. But how did it evolve in nature before it enters the human body? Researchers from institutions such as the Wuhan Institute of Virology at the Chinese Academy of Sciences published an article saying they found that the sequence of the new coronavirus and coronavirus (TG13) in bats is 96% identical. TG13 is by far the most similar strain to the new coronavirus gene; it is assumed that the bat is the natural host of a new species of coronavirus.
Other studies have also found that the new coronavirus resembles the genome sequence of the coronavirus, the carrier of which is the pangolin, especially in the region that binds receptors that allow the virus to enter the cell. This indicates that during the evolution of the new coronavirus, TG13 could recombine with the coronavirus, the carrier of which is a pangolin.
Despite the existing research results, many experts claim that the origin of the new coronavirus and its intermediate hosts is still difficult to determine, and full traceability of the virus can take a long time.
Stanley Perlman, a professor of microbiology and immunology at the University of Iowa in the United States, believes that animals that are intermediate hosts of the new virus can come from outside of China and be smuggled.
A WHO report on new coronavirus pneumonia (COVID-19), released in late February, states that “there are limitations in the available data, including; source of animal origin and natural host of the virus, the process of transmission of the virus to humans ”and so on. The epidemic is spreading on a global scale, and scientists do not yet have answers to many questions